from functools import reduce

def gcd(a, b):
    while b:
        a, b = b, a%b
    return a

def lcm(a, b):
	return a * b // gcd (a, b)

def extended_euclid(a, b):
    x1, y1, m = 1, 0, a
    x2, y2, n = 0, 1, b
    while m % n != 0:
        q, r = divmod(m, n)
        x1, y1, m, x2, y2, n = x2, y2, n, x1 - q * x2, y1 - q * y2, r
    return (x2, y2, n)

def fraenkel(A, M):
    '''
        solve
            x \equiv a_1 (mod m_1), ... x \equiv a_k (mod m_k)
        by applying the Fraenkel's Algorithm
        Input: 
            A = [a_1, ..., a_k]: a list
            M = [m_1, ..., m_k]: a list.
        Output:
            Returns the tuple (x, mod) of the solution x and the modulus mod = m_1 ... m_k if exists
            else (0, -1).
    '''
    # initialize
    x = 0
    mod = 1
    for a, m in zip(A, M):
        s, _, g = extended_euclid(mod, m)
        q, r = divmod(a - x, g)
        if r != 0:
            return (0, -1)
        temp = m // g
        u = (q * s) % (temp)
        x += mod * u
        mod *= temp
        x %= mod
    return (x, mod)

N = int(input())
MOD = 10**9 + 7
A = []
M = []
for _ in range(N):
    a, m = map(int, input().split())
    A.append(a)
    M.append(m)
x, m = chinese_reminder(A, M)
if (x, m) == (0, -1):
    x = -1
elif x == 0 and m != -1:
    x = reduce(lcm, M)
print(x % MOD if x != -1 else x)