#include <bits/stdc++.h>
using namespace std;

int main() 
{
    ifstream cin("fact.in");
    ofstream cout("fact.out");
	int p; cin >> p;
    int l = 0, r = 50;
    if (p == 0)
    {
        cout << 1;
        return 0;
    }
    for (int i = 2; i <= 60; i ++)
    {
        if (p == pow(5, i))
        {
            cout << -1;
            return 0;
        }
    }
    while (r - l > 1)
    {
        int mid = (l + r) / 2;
        if (pow(5, mid) <= 5 * p)
            l = mid;
        else
            r = mid;
    }
    cout << 5 * (p - l + 1);
}