#include <cstdio>
using namespace std;

int p;

int nr_zerouri(int nr)
{
    int rasp = 0;
    int put = 5;
    while (nr >= put)
    {
        rasp += nr / put;
        put *= 5;
    }
    return rasp;
}

int cautare_binara()
{
    int poz = 0;
    for (int pas = 1 << 20;pas >= 1;pas >>= 1)
        if (nr_zerouri(poz + pas) < p)
            poz += pas;
    return poz + 1;
}

void citire()
{
    freopen ("fact.in","r",stdin);
    freopen ("fact.out","w",stdout);
    scanf ("%d",&p);
}

int main()
{
    citire();
    printf("%d",cautare_binara());
    return 0;
}