#include <fstream>

using namespace std;

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

int n;
int zero;
int nr = 0, aux;

int main ()
{
    fin >> n;
    if (n == 0)
    fout << "1";
    else
    {
        while (zero < n)
        {
            nr = nr + 5;
            aux = nr;
            while (aux % 5 == 0)
            {
                zero++;
                aux = aux / 5;
            }
        }
        fout << nr;
    }
    fin.close ();
    fout.close ();
    return 0;
}