Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)


Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    if a2 < 10e-6:
        return [None, None], [None, None]
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            print(p1,p2)
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            print(ans, cnt1, cnt2)
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math
import sys

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b == 0:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b < 10e-6:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b < 10e-6:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 + a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 + a2*c2))/a2
    if b < 10e-6:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 + a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 + a2*c2))/a2
    if b < 10e-6:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b < 10e-6:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 10e-6:
        return [x1, y1], [x2, y2]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if b < 0.0001:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if b2**2 - a2*c2 < 0.0001:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 0.000001):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) < 10e-6:
        y1 = (o1[1] + o2[1])/2
        y2 = (o1[1] + o2[1])/2
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    if abs(b2**2 - a2*c2) < 10e-6:
        return [x1, y1], [None, None]
    else:
        return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 4):
                continue
            elif overlap(p[i], p[j], 10e-6):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        tmp = math.sqrt(1 - (x1 - o1[0])**2)
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 0
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2[0] != None and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 < d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2) or overlap(p[i], p[j], 1e-10):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [[x1, y1], [x2, y2]]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if dist(p[i], p[j]) > 2:
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if dist(p1, p[k]) <= 1:
                    cnt1 += 1
                if dist(p2, p[k]) <= 1:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1):
                    cnt1 += 1
                if overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 - d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
    x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if overlap(p[i], p[j], 2) > 0:
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if overlap(p1, p[k], 1) < 0:
                    cnt1 += 1
                if overlap(p2, p[k], 1) < 0:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)

Buggy python submission (verdict: Runtime Error):
import math

def overlap(p1, p2, d):
    return (p1[0] - p2[0])**2 + (p1[1] - p2[1])**2 <= d**2

def intersection(o1,o2):
    a  = 2*(o2[0] - o1[0])
    b  = 2*(o2[1] - o1[1])
    c  = (o1[0] - o2[0])*(o1[0] + o2[0]) + (o1[1] - o2[1])*(o1[1] + o2[1])
    a2 = a**2 + b**2
    b2 = a*c + a*b*o1[1] - b**2*o1[0]
    c2 = b**2*(o1[0]**2 + o1[1]**2 - 1) + c**2 + 2*b*c*o1[1]
    judge = b2**2 - a2*c2
    if judge < 0:
        return None, None
    elif abs(judge) < 1.0e-6:
        x = -b2/a2
        y = -(a*x + c)/b
        return [x,y], None
    else:
        x1 = (-b2 + math.sqrt(b2**2 - a2*c2))/a2
        x2 = (-b2 - math.sqrt(b2**2 - a2*c2))/a2
    if abs(b) == 0:
        y1 = o1[1] + math.sqrt(1 - (x1 - o1[0])**2)
        y2 = o1[1] - math.sqrt(1 - (x1 - o1[0])**2)
    else:
        y1 = -(a*x1 + c)/b
        y2 = -(a*x2 + c)/b
    return [x1, y1], [x2, y2]

while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            if not overlap(p[i], p[j], 2):
                continue
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1 and overlap(p1, p[k], 1):
                    cnt1 += 1
                if p2 and overlap(p2, p[k], 1):
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)



Fixed submission:
import math

def dist(p1, p2):
    return math.sqrt((p1[0] - p2[0])**2 + (p1[1] - p2[1])**2)

def intersection(o1,o2):
    if dist(o1,o2) > 2:
        p1, p2 =  [None, None], [None, None]
    elif dist(o1,o2) == 2:
        p1, p2 =  [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2], [None, None]
    else:
        m = [(o1[0] + o2[0])/2, (o1[1] + o2[1])/2]
        v = [m[0] - o1[0], m[1] - o1[1]]
        v_abs = dist(v,[0,0])
        w = [v[1], -v[0]]
        w_abs = dist(w,[0,0])
        n = [w[0]/w_abs, w[1]/w_abs]
        l = math.sqrt(1 - v_abs**2)
        p1 = [m[0] + l*n[0], m[1] + l*n[1]]
        p2 = [m[0] - l*n[0], m[1] - l*n[1]]
    return p1, p2
err = 1.0e-6
while True:
    n = int(input())
    if n == 0:
        break
    p = []
    for i in range(n):
        p.append(list(map(float, input().split(","))))
    ans = 1
    for i in range(n - 1):
        for j in range(i + 1, n):
            p1, p2 = intersection(p[i], p[j])
            cnt1 = 0
            cnt2 = 0
            for k in range(n):
                if p1[0] and dist(p1, p[k]) <= 1 + err:
                    cnt1 += 1
                if p2[0] and dist(p2, p[k]) <= 1 + err:
                    cnt2 += 1
            ans = max([ans, cnt1, cnt2])
    print(ans)