degreeof5

#include <iostream>

int degree5(int);

int main()
{
    int n = 5;
    while (n != 0)
    {
        std::cout << degree5(n) << std::endl;
        std::cin >> n;
    }
    return 0;
}

int degree5(int num)
{
    int k = 0;
    if (num == 1) return 0;
    else
    if (num % 5 != 0) return -1;
    else
    {
        k = degree5(num / 5);
        if (k == -1) return -1;
        else return k + 1;
    }
}