#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    long n, x = 0, f = 1;

    fin >> n;

    while (x < n)
    {
        int aux = f;
        while (aux % 5 == 0)
        {
            x++;
            aux /= 5;
        }

        f++;
    }

    f--;

    fout << f;

    return 0;
}