def inv_gcd(x,y):
    r0,r1,s0,s1 = x,y,1,0
    while r1:
        a,b = divmod(r0,r1)
        r0, r1, s0, s1 = r1, b, s1, s0-a*s1
    return s0%y,r0 # s0*x + ??*y = r0 = gcd(x,y)

def Chinese_remainder_theorem(r,m):
    assert len(r)==len(m)
    r0, M0 = 0,1
    for r1, M1 in zip(r,m):
        minv,g = inv_gcd(M0,M1)
        R = (r1-r0)%M1
        if R%g: return (0,0)
        r0 += R*minv%M1//g*M0
        M0 *= M1//g
    return r0,M0

MOD = 10**9+7
n = int(input())
x = [0]*n
y = [0]*n
for i in range(n):
    x[i],y[i] = map(int,input().split())

r,m = Chinese_remainder_theorem(x,y)
print(-1 if m == 0 else r%MOD if r else m%MOD)