#include <iostream>
#include <fstream>

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

int nrde0 (int x)
{
    int nr=0,i,aux,n;
    for (i=1;i<=x;i++)
    {
        aux=i;
        while(aux%5==0)
        {
            nr++;
            aux=aux/5;
        }
    }
    return nr;
}

int main()
{
    long p;
    f>>p;
    int ok=0,nr=1,n;
    while(ok==0)
    {
        if(nrde0(nr)==p)
        {
            ok=1;
            n=nr;
        }
        nr++;
    }
    g<<n;
    f.close();
    g.close();
    return 0;
}