#include<iostream>
#include<algorithm>
#include<fstream>
#include<cmath>

using namespace std;

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

int nr_fact(long x)
{
    int nr = 0,p=1;
    long i;
    for(i=0;i<=x;i+=5)
        if(i%10 == 0)
            nr++;
        else
        {
            if(i >= pow(5,p) && i < pow(5,p+1))
                nr++;
            else
            {
                p++;
                nr+=2;
            }
        }
    return nr-1;

}

int main()
{
    long N,P;
    bool ok = true;
    f>>P;

    N = P * 5;

    while(ok)
    {
        if(nr_fact(N-5) == P)
            N -= 5;
        else
            ok = false;
    }

    g<<N;




    f.close();
    g.close();
    return 0;

}