def safe_mod(x: int, m: int) -> int:
    x %= m
    if x < 0:
        x += m
    return x


def inv_gcd(a: int, b: int):
    a = safe_mod(a, b)
    if a == 0:
        return b, 0
    s, t = b, a
    m0, m1 = 0, 1

    while t:
        u = s // t
        s -= t * u
        m0 -= m1 * u
        s, t = t, s
        m0, m1 = m1, m0

    if m0 < 0:
        m0 += b // s
    return s, m0


def crt(r, m):
    assert len(r) == len(m)
    r0, m0 = 0, 1
    for r1, m1 in zip(r, m):
        assert m1 >= 1
        if m0 < m1:
            r0, r1 = r1, r0
            m0, m1 = m1, m0

        if m0 % m1 == 0:
            if r0 % m1 != r1:
                return 0, 0
            continue

        g, im = inv_gcd(m0, m1)
        u1 = m1 // g

        if (r1 - r0) % g != 0:
            return 0, 0

        x = ((r1 - r0) // g % u1) * im % u1
        r0 += x * m0
        m0 *= u1
        if r0 < 0:
            r0 += m0

    return r0, m0


# ---- main相当 ----
import sys

input = sys.stdin.readline
n = int(input())
r = [0] * n
m = [0] * n
for i in range(n):
    r[i], m[i] = map(int, input().split())

ans_r, ans_m = crt(r, m)

if ans_m == 0:
    print(-1)
else:
    if ans_r == 0:
        ans_r += ans_m
    print(ans_r % 1000000007)