def exgcd(a, b):
	p = 1; q = 0; r = 0; s = 1;
	while b > 0:
		c = a//b
		d = a; a = b; b = d % b;
		d = p; p = q; q = d - c * q;
		d = r; r = s; s = d - c * s;
	return (a, p, r)

def crt(p, m, q, n):
	a,d,r = exgcd(p, q)
	if (n-m) % a != 0: return (-1,-1)
	mod = p*(q//a)
	a = (d*((n-m)//a)*p+m)%mod
	if a < 0: a += mod
	return (a,mod)

import sys
n = int(input())
xx = 0; yy = 1;
for _ in range(n):
	x,y = map(int,input().split())
	xx,yy = crt(y, x, yy, xx)
	if xx == -1:
		print(-1)
		sys.exit(0)
if xx == 0:
	xx = yy
print(xx % 1000000007)