#include <iostream>
#include <fstream>

using namespace std;

ifstream f("fact.in");
ofstream g("fact.out");

int n, nrZero = 0, aux = 0;

int main()
{
    f>>n;
    if(n == 0)
    {
        g<<1;
        return 0;
    }


    while(nrZero < n)
    {
        aux += 5;
        nrZero = aux / 5 + aux / 25 + aux / 125 + aux / 625 + aux / 3125 + aux / 15625 + aux / 78125;
    }
    g<<aux;

    return 0;
}