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

ifstream fin("fact.in");
ofstream fout("fact.out");

int n;
int found = 0;

int main()
{
    fin >> n;

    if(n == 0){
        fout << 1;
        ++found;
    }

    int n5 = 0, rez = 1;
    while(n5 < n && !found){
        int cp = rez;
        while(cp % 5 == 0){
            cp /= 5;
            n5++;
        }
        rez++;
    }

    rez--;

    if(n5 == n){
        fout << rez;
    }else if(n5 > n){
        fout << -1;
    }
}