//
//  main.cpp
//  ex2
//
//  Created by Alexandru Bagu on 02.10.2013.
//  Copyright (c) 2013 Alexandru Bagu. All rights reserved.
//

#include <iostream>
#include <fstream>
using namespace std;
typedef long long int ulint;
int main(int argc, const char * argv[])
{
    ifstream fin("fact.in");
    int k;
    fin>>k;
    ulint n = 0;
    ulint m = 0;
    ulint aux = 0;
    while(m < k)
    {
        n++;
        aux = n;
        while(aux % 5 == 0)
            aux/=5, m++;
    }
    ofstream fout("fact.out");
    fout<<n<<endl;
    return 0;
}