Buggy python submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline
from math import sqrt
from itertools import combinations

N = int(input())
xy = [[int(i) for i in input().split()] for _ in range(N)]
E = 1e-9

def vnrm(v) :
  d = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2])
  for i in range(3) :
    v[i] /= d

  return d

def vrot90(v) :
  v0 = v[0]
  v[0] = -v[1]
  v[1] =  v0

def calc(x1, y1, x2, y2, x3, y3) :
  c = [0] * 3
  v123 = (x2-x1)*(x3-x2) + (y2-y1)*(y3-y2)
  v231 = (x3-x2)*(x1-x3) + (y3-y2)*(y1-y3)
  v312 = (x1-x3)*(x2-x1) + (y1-y3)*(y2-y1)

  if v123 < 0 and v231 < 0 and v312 < 0 :
    x12 = (x1+x2)/2
    y12 = (y1+y2)/2
    v12 = [x2-x1, y2-y1, 0.]
    vnrm(v12)
    vrot90(v12)
    x13 = (x1+x3)/2
    y13 = (y1+y3)/2
    v13 = [x3-x1, y3-y1, 0.]
    vnrm(v13)
    vrot90(v13)
    d = -(v12[0]*v13[1] - v12[1]*v13[0])
    ds = -(x13-x12)*v13[1] + (y13-y12)*v13[0]
    s = ds/d
    c[0] = x12 + s*v12[0]
    c[1] = y12 + s*v12[1]
    c[2] = sqrt((x1-c[0])*(x1-c[0]) + (y1-c[1])*(y1-c[1]))
  
  else :
    if v123 >= 0 :
      c[0] = (x1+x3)/2
      c[1] = (y1+y3)/2
      c[2] = sqrt((x1-x3)*(x1-x3) + (y1-y3)*(y1-y3))/2
    elif v231 >= 0 :
      c[0] = (x1+x2)/2
      c[1] = (y1+y2)/2
      c[2] = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))/2
    else :
      c[0] = (x2+x3)/2
      c[1] = (y2+y3)/2
      c[2] = sqrt((x2-x3)*(x2-x3) + (y2-y3)*(y2-y3))/2

  return c

ret = float('inf')
for (i, j, k) in combinations(range(N), 3) :
  cx, cy, cr = calc(*xy[i], *xy[j], *xy[k])
  for x, y in xy :
    if sqrt((cx - x) ** 2 + (cy - y) ** 2) > cr + E :
      break
  else :
    ret = min(ret, cr)
    
if N == 2 :
  r = sqrt((xy[0][0] - xy[1][0]) ** 2 + (xy[0][1] - xy[1][1]) ** 2)
  print(r / 2)

else :
  print(ret)

Fixed submission:
import sys
input = sys.stdin.readline
from math import sqrt
from itertools import combinations

N = int(input())
xy = [[int(i) for i in input().split()] for _ in range(N)]
E = 1e-9

def vnrm(v) :
  d = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2])
  for i in range(3) :
    v[i] /= d

  return d

def vrot90(v) :
  v0 = v[0]
  v[0] = -v[1]
  v[1] =  v0

def calc(x1, y1, x2, y2, x3, y3) :
  c = [0] * 3
  v123 = (x2-x1)*(x3-x2) + (y2-y1)*(y3-y2)
  v231 = (x3-x2)*(x1-x3) + (y3-y2)*(y1-y3)
  v312 = (x1-x3)*(x2-x1) + (y1-y3)*(y2-y1)

  if v123 < 0 and v231 < 0 and v312 < 0 :
    x12 = (x1+x2)/2
    y12 = (y1+y2)/2
    v12 = [x2-x1, y2-y1, 0.]
    vnrm(v12)
    vrot90(v12)
    x13 = (x1+x3)/2
    y13 = (y1+y3)/2
    v13 = [x3-x1, y3-y1, 0.]
    vnrm(v13)
    vrot90(v13)
    d = -(v12[0]*v13[1] - v12[1]*v13[0])
    ds = -(x13-x12)*v13[1] + (y13-y12)*v13[0]
    s = ds/d
    c[0] = x12 + s*v12[0]
    c[1] = y12 + s*v12[1]
    c[2] = sqrt((x1-c[0])*(x1-c[0]) + (y1-c[1])*(y1-c[1]))
  
  else :
    if v123 >= 0 :
      c[0] = (x1+x3)/2
      c[1] = (y1+y3)/2
      c[2] = sqrt((x1-x3)*(x1-x3) + (y1-y3)*(y1-y3))/2
    elif v231 >= 0 :
      c[0] = (x1+x2)/2
      c[1] = (y1+y2)/2
      c[2] = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))/2
    else :
      c[0] = (x2+x3)/2
      c[1] = (y2+y3)/2
      c[2] = sqrt((x2-x3)*(x2-x3) + (y2-y3)*(y2-y3))/2

  return c

ret = float('inf')
for (i, j, k) in combinations(range(N), 3) :
  cx, cy, cr = calc(xy[i][0], xy[i][1], xy[j][0], xy[j][1], xy[k][0], xy[k][1])
  for x, y in xy :
    if sqrt((cx - x) ** 2 + (cy - y) ** 2) > cr + E :
      break
  else :
    ret = min(ret, cr)
    
if N == 2 :
  r = sqrt((xy[0][0] - xy[1][0]) ** 2 + (xy[0][1] - xy[1][1]) ** 2)
  print(r / 2)

else :
  print(ret)

Buggy python submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**5)
from math import sqrt
from itertools import combinations

N = int(input())
xy = [[int(i) for i in input().split()] for _ in range(N)]
E = 1e-9

def vnrm(v) :
    d = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2])
    for i in range(3) :
      v[i] /= d

    return d

def vrot90(v) :
    v0 = v[0]
    v[0] = -v[1]
    v[1] =  v0

def calc(x1, y1, x2, y2, x3, y3) :# 3点の最小包含円
  c = [0] * 3
  v123 = (x2-x1)*(x3-x2) + (y2-y1)*(y3-y2)
  v231 = (x3-x2)*(x1-x3) + (y3-y2)*(y1-y3)
  v312 = (x1-x3)*(x2-x1) + (y1-y3)*(y2-y1)

  if v123 < 0 and v231 < 0 and v312 < 0 :
    x12 = (x1+x2)/2
    y12 = (y1+y2)/2
    v12 = [x2-x1, y2-y1, 0.]
    vnrm(v12)
    vrot90(v12)
    x13 = (x1+x3)/2
    y13 = (y1+y3)/2
    v13 = [x3-x1, y3-y1, 0.]
    vnrm(v13)
    vrot90(v13)
    d = -(v12[0]*v13[1] - v12[1]*v13[0])
    ds = -(x13-x12)*v13[1] + (y13-y12)*v13[0]
    s = ds/d
    c[0] = x12 + s*v12[0]
    c[1] = y12 + s*v12[1]
    c[2] = sqrt((x1-c[0])*(x1-c[0]) + (y1-c[1])*(y1-c[1]))
  
  else :
    if v123 >= 0 :
      c[0] = (x1+x3)/2
      c[1] = (y1+y3)/2
      c[2] = sqrt((x1-x3)*(x1-x3) + (y1-y3)*(y1-y3))/2
    elif v231 >= 0 :
      c[0] = (x1+x2)/2
      c[1] = (y1+y2)/2
      c[2] = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))/2
    else :
      c[0] = (x2+x3)/2
      c[1] = (y2+y3)/2
      c[2] = sqrt((x2-x3)*(x2-x3) + (y2-y3)*(y2-y3))/2

  return c

ret = float('inf')
for (i, j, k) in combinations(range(N), 3) :
  cx, cy, cr = calc(*xy[i], *xy[j], *xy[k])
  for x, y in xy :
    if sqrt((cx - x) ** 2 + (cy - y) ** 2) > cr + E :
      break
  else :
    ret = min(ret, cr)
    
if N == 2 :
  r = sqrt((xy[0][0] - xy[1][0]) ** 2 + (xy[0][1] - xy[1][1]) ** 2)
  print(r / 2)

else :
  print(ret)

Fixed submission:
import sys
input = sys.stdin.readline
from math import sqrt
from itertools import combinations

N = int(input())
xy = [[int(i) for i in input().split()] for _ in range(N)]
E = 1e-9

def vnrm(v) :
  d = sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2])
  for i in range(3) :
    v[i] /= d

  return d

def vrot90(v) :
  v0 = v[0]
  v[0] = -v[1]
  v[1] =  v0

def calc(x1, y1, x2, y2, x3, y3) :
  c = [0] * 3
  v123 = (x2-x1)*(x3-x2) + (y2-y1)*(y3-y2)
  v231 = (x3-x2)*(x1-x3) + (y3-y2)*(y1-y3)
  v312 = (x1-x3)*(x2-x1) + (y1-y3)*(y2-y1)

  if v123 < 0 and v231 < 0 and v312 < 0 :
    x12 = (x1+x2)/2
    y12 = (y1+y2)/2
    v12 = [x2-x1, y2-y1, 0.]
    vnrm(v12)
    vrot90(v12)
    x13 = (x1+x3)/2
    y13 = (y1+y3)/2
    v13 = [x3-x1, y3-y1, 0.]
    vnrm(v13)
    vrot90(v13)
    d = -(v12[0]*v13[1] - v12[1]*v13[0])
    ds = -(x13-x12)*v13[1] + (y13-y12)*v13[0]
    s = ds/d
    c[0] = x12 + s*v12[0]
    c[1] = y12 + s*v12[1]
    c[2] = sqrt((x1-c[0])*(x1-c[0]) + (y1-c[1])*(y1-c[1]))
  
  else :
    if v123 >= 0 :
      c[0] = (x1+x3)/2
      c[1] = (y1+y3)/2
      c[2] = sqrt((x1-x3)*(x1-x3) + (y1-y3)*(y1-y3))/2
    elif v231 >= 0 :
      c[0] = (x1+x2)/2
      c[1] = (y1+y2)/2
      c[2] = sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2))/2
    else :
      c[0] = (x2+x3)/2
      c[1] = (y2+y3)/2
      c[2] = sqrt((x2-x3)*(x2-x3) + (y2-y3)*(y2-y3))/2

  return c

ret = float('inf')
for (i, j, k) in combinations(range(N), 3) :
  cx, cy, cr = calc(xy[i][0], xy[i][1], xy[j][0], xy[j][1], xy[k][0], xy[k][1])
  for x, y in xy :
    if sqrt((cx - x) ** 2 + (cy - y) ** 2) > cr + E :
      break
  else :
    ret = min(ret, cr)
    
if N == 2 :
  r = sqrt((xy[0][0] - xy[1][0]) ** 2 + (xy[0][1] - xy[1][1]) ** 2)
  print(r / 2)

else :
  print(ret)