#include <fstream>
#include <algorithm>
#include <iostream>
#include <math.h>
using namespace std;

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

long long int n,ap=0,i,j,ap1=0;

bool ok=true;

int main()
{
    fin>>n;
    i=1;
    ok=true;
    int x;
    while(ap!=n)
    {
        i++;
        if(i%5==0)
        {
            x=i;
            while(x%5==0)
            {
                ap++;
                x=x/5;
            }
        }
    }
    fout<<i;
    return 0;
}