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

class Main {

    public static void main(String[] args) throws IOException {

        Scanner reader = new Scanner(new FileInputStream("fact.in"));

        int p = reader.nextInt();
        int N = 1;

        if (p > 0) {
            int step = 1;
            do {
                if (step % 5 == 0) p -= (factorsOfFiveIn(step) + 1);
                else p -= 1;
                step += 1;
            } while (p > 0);
            N = step * 5 - 5;
        }

        BufferedWriter writer = new BufferedWriter(new FileWriter("fact.out"));
        writer.write(String.valueOf(N));
        writer.close();
        reader.close();
    }

    private static int factorsOfFiveIn(int step) {
        System.out.println("searching a factor for " + step);
        int count = 1;
        int mult = 25;
        while (step % mult != step) {
            ++count;
            mult *= 5;
        }

        return count;
    }

}