#!/usr/bin/env python3
import sys
input = sys.stdin.readline
from fractions import gcd

n = int(input())
m = int(input())
base = m // gcd(n, m)
while base % 2 == 0:
    base //= 2
while base % 5 == 0:
    base //= 5

if base == 1:
    s = str(n / m)
    if "e" in s:
        index = s.find("e") - 1
    else:
        index = len(s) - 1
    while s[index] in ".0":
        index -= 1
    print(s[index])
else:
    print(-1)