'''
中国剩余定理应用
'''

# 求a, b最大公约数，同时求出裴蜀定理中的一组系数x, y， 满足x*a + y*b = gcd(a, b)
def exp_gcd(a, b):
    flag = True
    if a > b:
        flag = False
        a, b = b, a

    if a == 0:
        return (b, 0, 1) if flag else (b, 1, 0)

    gcd_val, x, y = exp_gcd(b%a, a)
    new_x = y - x * (b // a)
    new_y = x
    return (gcd_val, new_x, new_y) if flag else (gcd_val, new_y, new_x)


# 求val对mod取模的逆元, 也就是(val * ans) 和 1 对 mod 求模同余
def get_mul_mod_rev_meta(val, mod):
    gcd_val, x, _ = exp_gcd(val, mod)
    return None if gcd_val != 1 else x

n = int(input())

a_arr = []
m_arr = []
M = 1
for i in range(n):
    m, a = map(int, input().split())
    m_arr.append(m)
    a_arr.append(a)
    M *= m

ans = 0
for i in range(n):
    ans += (a_arr[i] * (M // m_arr[i]) * get_mul_mod_rev_meta(M // m_arr[i], m_arr[i])) % M
    ans %= M
print(ans)