from math import gcd
from bisect import bisect_left, bisect_right
from heapq import heappop, heappush
from collections import defaultdict, deque, Counter
import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline


def extgcd(a, b):
    if b == 0:
        return 1, 0, a
    q, r = a//b, a % b
    x, y, d = extgcd(b, r)
    s, t = y, x-y*q
    return s, t, d

def crt(b, m):
    r = 0
    M = 1
    for i in range(len(b)):
        s,t, d = extgcd(M, m[i])
        if (b[i] - r) % d != 0: 
            return [0, -1]
        lcm = M * m[i] // d
        r +=  M * ((b[i] - r) // d) * s
        M = lcm
        r %= M
    return r, M

n = int(input())   
b = []
m = []
for i in range(n):
    x,y = map(int,input().split())
    b.append(x)
    m.append(y)
r, M = crt(b,m)
if M != -1 and r != 0:
    print(r)
else:
    print(M)