import sys

# cf
# http://techtipshoge.blogspot.com/2015/02/blog-post_15.html

def gcd(a, b):
    if b == 0:
        return a
    return gcd(b, a%b)

# return [g, x, y]
# g = gcd(a, b)
# x, y satisfies a x + b y = g
def extgcd(a, b):
    if b == 0:
        return [a, 1, 0]
    g, x, y = extgcd(b, a%b)
    return [g, y, x - a/b * y]

# eq0: x = a0 (mod m0)
# eq1: x = a1 (mod m1)
# returns [xt, mod] such that x = xt + k mod for integer k.
def crt(eq0, eq1):
    a0, m0 = eq0
    a1, m1 = eq1

    g = gcd(m0, m1)

    if a0 % g != a1 % g:
        #raise Exception("x doesn't exist.")
        print(-1)
        sys.exit()

    if g > 1:
        m0 /= g
        m1 /= g

        while True:
            gt = gcd(m0, g)
            if gt == 1:
                break
            m0 *= gt
            g /= gt
        
        m1 *= g

        a0 %= m0
        a1 %= m1

    g, p, q = extgcd(m0, m1)
    
    x = a0 * q * m1 + a1 * p * m0
    mod = m0 * m1
    x = x % mod

    return [x, mod]

n = int(raw_input())
eqs = []
for _ in xrange(n):
    a, m = map(int, raw_input().split())
    eqs.append((a, m))

# solve the system
x, mod = reduce(crt, eqs, (0, 1))
if x==0:
    x += mod

MOD = 1000000007
print(x % MOD)