package com.company;

import java.io.*;
import java.util.Scanner;

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 {
            Scanner reader = new Scanner(new FileInputStream("factorial.in"));
            int nr = reader.nextInt();
            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;
            PrintWriter writer = new PrintWriter("factorial.out");
            writer.write(Integer.toString(i));
            writer.close();
            reader.close();


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