import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

from fractions import gcd

#処理内容
def main():
	N = int(input())
	M = int(input())
	GCD = gcd(N, M)
	n, m = int(N // GCD), int(M // GCD)
	mm = m
	cnt2, cnt5 = 0, 0
	while True:
		if mm % 2 == 0:
			mm = int(mm // 2)
			cnt2 += 1
		else:
			break

	while True:
		if mm % 5 == 0:
			mm = int(mm // 5)
			cnt5 += 1
		else:
			break

	if mm != 1:
		print(-1)
		return

	if cnt2 < cnt5:
		for i in range(cnt5 - cnt2):
			n *= 2
	else:
		for i in range(cnt2 - cnt5):
			n *= 5

	n = list(reversed(str(n)))
	for i in n:
		if i != "0":
			print(i)
			return




if __name__ == '__main__':
	main()