#include <iostream>
#include<fstream>
#include<cstring>
#include<algorithm>
#include<iomanip>
#define N 100005
using namespace std;

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

//suma exp put 5=p

int p;

void solve()
{
    int i,ct=0,x=1,cx;
    while(ct!=p)
    {
        x++;cx=x;
        while(cx%5==0)cx/=5,ct++;

    }
    fout<<x;
}

int main()
{
    fin>>p;
    solve();


    return 0;
}