from math import gcd


def linear_congruence(a: int, b: int, m: int) -> tuple[int, int] | tuple[None, None]:
    # a x = b (mod m)
    g = gcd(a, m)
    if b % g != 0:
        return None, None

    a2 = a // g
    b2 = b // g
    m2 = m // g
    # a' x = b' (mod m')
    x = b2 * pow(a2, -1, m2) % m2
    return x, m2


def crt2(r1, m1, r2, m2):
    # x = r1 (mod m1)
    # x = r1 + m1 t
    # r1 + m1 t = r2 (mod m2)
    # m1 t = r2 - r1 (mod m2)

    t, m = linear_congruence(m1, r2 - r1, m2)
    if t is None:
        return None, None

    x = r1 + m1 * t
    mod = m1 * m
    return x % mod, mod


def crt3(r1, m1, r2, m2, r3, m3):
    r, m = crt2(r1, m1, r2, m2)
    if r is None:
        return None, None

    r, m = crt2(r, m, r3, m3)
    return r, m


def crt(rms: list[tuple[int, int]]) -> tuple[int, int] | tuple[None, None]:
    r = 0
    m = 1
    for nr, nm in rms:
        r, m = crt2(r, m, nr, nm)
        if r is None:
            return None, None

    return r, m


MOD = 10**9 + 7
N = int(input())

rms = []
for _ in range(N):
    X, Y = map(int, input().split())
    rms.append((X, Y))

r, m = crt(rms)
if r is None:
    print(-1)
elif r == 0:
    print(m % MOD)
else:
    print(r % MOD)