package com.company;

import java.io.*;

public class Main {
    public static int count5(int n){
        int nr=0, c5=0;
        while (n%5==0){
            c5++;
            n/=5;
        }
        return c5;
    }

    public static int count2(int n){
        int nr=0, c2=0;
        while (n%2==0){
            c2++;
            n/=2;
        }
        return c2;
    }

    public static void main(String[] args) {
        FileReader fr= null;
        String fn="factorial.in";
        String fn2="factorial.out";
        try {
            fr = new FileReader(fn);
            BufferedReader br=new BufferedReader(fr);
            String line=br.readLine();
            int nr=Integer.parseInt(line);
            int n=0;
            int i=1, c2=0, c5=0;
            do{
                if(i%2==0)
                    c2=c2+Main.count2(i);

                if (i%5==0)
                    c5=c5+Main.count5(i);
                n=Math.min(c2, c5);
                i++;
            }
            while (n<nr);
            i-=1;
            FileWriter fw=new FileWriter(fn2);
            BufferedWriter bw=new BufferedWriter(fw);
            bw.write(Integer.toString(i));
            br.close();
            bw.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}