# 1
from math import gcd, sqrt

prime = [True] * 100001

def sieve() :
    prime[0] = False
    prime[1] = False
    
    for p in range(2, int(sqrt(100001)) + 1) :
        if prime[p] == True :
            for i in range(p**2, 100001, p) :
                prime[i] = False
                
def common_prime(a, b) :

    __gcd = gcd(a, b)
    result = []
    for i in range(2, __gcd + 1) :
        if prime[i] and __gcd % i == 0 :
            result.append(i)
    if result:
        return max(result)
    else:
        return -1

if __name__ == "__main__" :
    sieve()
    a, b = int(input()), int(input())
    print(common_prime(a, b))

# 2
n = int(input())
n1, n2 = 0, 0
if not n&1:
    for i in range(n//2):
        n1 = (n1*10)+9
    print(2*n1)
else:
    for i in range(n//2):
        n2 = (n2*10)+9
    print(n2+(n2*10+9))

# 3
def solve(l, m):
    n = len(l)
    s = 0
    j = n - 1
    for i in range(m, -1, -1):
        s += l[i]*j
        j -= 1
    j = 0
    for i in range(m+1, n):
        s += l[i] * j
        j += 1
    return s
    
    
n, l = int(input()), list(map(int, input().split()))
m = 0
for i in range(n):
    m = max(m, solve(l, i))
    
print(m)