def count_factors(k, p):
    res = 0
    while k > 0:
        k = k // p
        res += k
    return res

n, m = map(int, input().split())

count_2_n = count_factors(n, 2)
count_5_n = count_factors(n, 5)
count_2_m = count_factors(m, 2)
count_5_m = count_factors(m, 5)

total_2 = count_2_n + count_2_m
total_5 = count_5_n + count_5_m

print(min(total_2, total_5))