Problem p03061 (python)

Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LS()
    return l
sys.setrecursionlimit(1000000)
mod = 1000000007

#A
def A():
    a,b,t = LI()
    k = t//a
    print(k*b)
    return

#B
def B():
    n = I()
    v = LI()
    c = LI()
    ans = 0
    for i in range(n):
        if v[i] > c[i]:
            ans += (v[i]-c[i])
    print(ans)
    return

#C
def C():
    def gcd(a,b):
        if a == 0:
            return b
        return gcd(b%a, a)
    n = I()
    a = LI()
    if n <= 1000:
        ans = 1
        for i in range(n):
            b = a[:i]+a[i+1:]
            g = b[0]
            for j in b[1:]:
                g = gcd(g,j)
            ans = max(ans,g)
        print(ans)
    else:
        m = math.ceil(n**0.5)
        while len(a) < m**2:
            n += 1
            a.append(a[-1])
        f = [0 for i in range(m)]
        for i in range(m):
            b = a[m*i:m*(i+1)]
            g = b[0]
            for j in b[1:]:
                g = gcd(g,j)
            f[i] = g
        ans = 1
        for i in range(n):
            j = i//m
            c = f[:j]+f[j+1:]+a[m*j:i]+a[i+1:m*(j+1)]
            g = c[0]
            for k in c[1:]:
                g = gcd(g, k)
            ans = max(ans,g)
        print(ans)
    return

#D
def D():
    n = I()
    a = LI()
    k = 0
    for i in a:
        if i < 0:
            k += 1
    ans = 0
    m = float("inf")
    for i in a:
        ans += abs(i)
        m = min(m,abs(i))
    if k%2:
        ans -= 2*m
    print(ans)
    return


#Solve
if __name__ == "__main__":
    C()

Buggy submission (verdict: Runtime Error):
class SegmentTree:
    def __init__(self, size, f=lambda x,y : x+y, default=0):
        self.size = 2**(size-1).bit_length()
        self.default = default
        self.dat = [default]*(self.size*2-1)
        self.f = f

    def update(self, i, x):
        i += self.size-1
        self.dat[i] = x
        while i > 0:
            i = (i-1) >> 1
            self.dat[i] = self.f(self.dat[i*2+1], self.dat[i*2+2])

    def query(self, l, r, k=0, L=0, R=None):
        if R is None:
            R = self.size
        if R <= l or r <= L:
            return self.default
        if l <= L and R <= r:
            return self.dat[k]
        else:
            lres = self.query(l, r, k*2+1, L, (L+R) >> 1)
            rres = self.query(l, r, k*2+2, (L+R) >> 1, R)
            return self.(lres, rres)

def gcd(a, b):
    if a == 0:
        return b
    else:
        return gcd(b%a, a)

n = int(input())
a = list(map(int, input().split()))
s = SegmentTree(n, gcd)
for i in range(n):
    s.update(i, a[i])

ans = 1
for i in range(n):
    left = s.query(0, i)
    right = s.query(i+1, n)
    res = gcd(left, right)
    if ans < res:
        ans = res
print(ans)