"""

時刻tを求める

X <= t < X+Y (mod 2X+2Y)
P <= t (mod P+Q)

それぞれに関して中国剰余

"""

import sys
from sys import stdin

import math
def extGCD(a,b):
    g = math.gcd(a,b)
    x, y, u, v = 1, 0, 0, 1
    while b:
        k = a // b
        x -= k * u
        y -= k * v
        x, u = u, x
        y, v = v, y
        a, b = b, a % b
    return g ,x, y

def crt2(b1,m1,b2,m2):
    g,p,q = extGCD(m1,m2)
    if b1 % g != b2 % g:
        return 0,0
    return ( b1 + m1 * ((b2-b1)//g) * p ) % (m1*m2//g) , m1*m2//g

def crt(b,m):
    assert len(b) == len(m)
    
    nb,nm = 0,1
    for i in range(len(b)):
        nb,nm = crt2(nb,nm,b[i],m[i])
        if (nb,nm) == (0,0):
            return (0,0)
    return nb,nm


TT = 1
mod = 10**9+7
for loop in range(TT):

    N = int(stdin.readline())
    B = []
    M = []

    for i in range(N):
        x,y = map(int,stdin.readline().split())
        B.append(x)
        M.append(y)

    ans,lcm = crt(B,M)
    if (ans,lcm) == (0,0):
        print (-1)
    elif ans == 0:
        print (lcm % mod)
    else:
        print (ans % mod)