Buggy python submission (verdict: Runtime Error):
def distance(a,b,c,d):
    return ((c-a)**2+(d-b)**2)**(1/2)
def sankaku(a,b,c,d,e,f):
    S=1/2*abs((c-a)*(f-b)-(e-a)*(d-b))
    return (distance(a,b,c,d)*distance(c,d,e,f)*distance(e,f,a,b))/(4*S)
from itertools import combinations
n=int(input())
XY=[list(map(int,input().split()))for i in range(n)]
if n>=3:
    kumiawase=list(combinations(range(n),3))
    ans=0
    for tu in kumiawase:
        p,q = XY[tu[0]]
        r,s = XY[tu[1]]
        t,u = XY[tu[2]]
        ans=max(ans,sankaku(p,q,r,s,t,u))
    print(ans)
else:
    ans=distance(XY[0][0],XY[0][1],XY[1][0],XY[1][1])
    print(ans)

Fixed submission:
n = int(input())
XY = []
for i in range(n):
    x, y = map(int, input().split())
    XY.append((x, y))


# 外積、平行判定
def cross(a, b):
    return a.real * b.imag - b.real * a.imag


# 内積、直行判定
def dot(a, b):
    return a.real * b.real + a.imag * b.imag


# 外心の中心
def circumcenter(a, b, c):
    bunshi = (a - b) * dot(c, c) + (b - c) * dot(a, a) + (c - a) * dot(b, b)
    bunbo = (a - b) * c.conjugate() + (b - c) * a.conjugate() + (c - a) * b.conjugate()
    if bunbo == 0:
        return False, 0
    return True, bunshi / bunbo


kouho = []
for i in range(n - 1):
    a, b = XY[i]
    z1 = complex(a, b)
    for j in range(i + 1, n):
        c, d = XY[j]
        z2 = complex(c, d)
        kouho.append((z1 + z2) / 2)
if n >= 3:
    for i in range(n - 2):
        a, b = XY[i]
        z1 = complex(a, b)
        for j in range(i + 1, n - 1):
            c, d = XY[j]
            z2 = complex(c, d)
            for k in range(j + 1, n):
                e, f = XY[k]
                z3 = complex(e, f)
                flag, gaishin = circumcenter(z1, z2, z3)
                if flag:
                    kouho.append(gaishin)
ans = 10 ** 10
for z in kouho:
    temp = 0
    for i in range(n):
        x, y = XY[i]
        z1 = complex(x, y)
        temp = max(temp, abs(z - z1))
    ans = min(ans, temp)
print(ans)

Buggy python submission (verdict: Runtime Error):
def distance(a,b,c,d):
    return ((c-a)**2+(d-b)**2)**(1/2)
def sankaku(a,b,c,d,e,f):
    if ac+bd==0:
        return 1/2*distance(a,b,c,d)
    elif ce+df==0:
        return 1/2*distance(c,d,e,f)
    elif ea+bf==0:
        return 1/2 * distance(e,f,a,b)
    else:
        S=1/2*abs((c-a)*(f-b)-(e-a)*(d-b))
        return (2*S)/((distance(a,b,c,d)+distance(c,d,e,f)+distance(e,f,a,b)))
from itertools import combinations
n=int(input())
XY=[list(map(int,input().split()))for i in range(n)]
if n>=3:
    kumiawase=list(combinations(range(n),3))
    ans=0
    for tu in kumiawase:
        p,q = XY[tu[0]]
        r,s = XY[tu[1]]
        t,u = XY[tu[2]]
        ans=max(ans,sankaku(p,q,r,s,t,u))
    print(ans)
else:
    ans=distance(XY[0][0],XY[0][1],XY[1][0],XY[1][1])
    print(ans)

Fixed submission:
n = int(input())
XY = []
for i in range(n):
    x, y = map(int, input().split())
    XY.append((x, y))


# 外積、平行判定
def cross(a, b):
    return a.real * b.imag - b.real * a.imag


# 内積、直行判定
def dot(a, b):
    return a.real * b.real + a.imag * b.imag


# 外心の中心
def circumcenter(a, b, c):
    bunshi = (a - b) * dot(c, c) + (b - c) * dot(a, a) + (c - a) * dot(b, b)
    bunbo = (a - b) * c.conjugate() + (b - c) * a.conjugate() + (c - a) * b.conjugate()
    if bunbo == 0:
        return False, 0
    return True, bunshi / bunbo


kouho = []
for i in range(n - 1):
    a, b = XY[i]
    z1 = complex(a, b)
    for j in range(i + 1, n):
        c, d = XY[j]
        z2 = complex(c, d)
        kouho.append((z1 + z2) / 2)
if n >= 3:
    for i in range(n - 2):
        a, b = XY[i]
        z1 = complex(a, b)
        for j in range(i + 1, n - 1):
            c, d = XY[j]
            z2 = complex(c, d)
            for k in range(j + 1, n):
                e, f = XY[k]
                z3 = complex(e, f)
                flag, gaishin = circumcenter(z1, z2, z3)
                if flag:
                    kouho.append(gaishin)
ans = 10 ** 10
for z in kouho:
    temp = 0
    for i in range(n):
        x, y = XY[i]
        z1 = complex(x, y)
        temp = max(temp, abs(z - z1))
    ans = min(ans, temp)
print(ans)