#include <bits/stdc++.h>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

/*
vrem o functie care ia ca parametru un numar naturla N, si intoarce 
cate 0-uri are N! 
*/

int cate_zerouri(unsigned int N)
{
    int s=0, nr, i = 5;
    
    while(i <= N)
    {
        s = s + N / i;
        i = i * 5;
    }

    return s;
}

int main()
{
    int P, s;
    fin >> P;

    for(int i = 1; i <= INT_MAX; i++)
    {
        s = cate_zerouri(i);
        if (s == P)
        {
            fout << i;
            break;
        }
        if (s > P)
        {
            fout << -1;
            break;
        }
    }


    return 0;
}