백준 2004번(python)

 

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def div_number(k, n):
    count = 0
    while(k != 0):
        k = k // n
        count += k
    return count

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

div_five = div_number(n, 5) - div_number(m, 5) - div_number(n-m, 5)
div_two = div_number(n, 2) - div_number(m, 2) - div_number(n-m, 2)

print(min(div_five, div_two))