def CRT(BMlist):
    # Extended Euclidean Algorithm
    def extgcd(a, b):
        if b:
            d, y, x = extgcd(b, a % b)
            y -= (a // b)*x
            return d, x, y
        return a, 1, 0
    r = 0; M = 1
    for b,m in BMlist:
        d,p,q = extgcd(M,m)
        if (b-r)%d != 0:
            return 0,-1
        r += M*((b-r)//d*p%(m//d))
        M *= m//d
    return r,M

import math
BMlist = []
ans = 1
sml = 10**9+7
N = int(input())
for i in range(N):
    x,y = map(int, input().split())
    BMlist.append((x,y))
    g = math.gcd(ans,y)
    ans = ((ans*y)//g)
r,m = CRT(BMlist)
if (r,m) == (0,-1):
    r = -1
elif r == 0 and m != -1:
    r = ans
print(r % sml if r != -1 else r)