import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
	// write your code here
        Scanner s = new Scanner(System.in);
        long count = 0;
        long N = s.nextLong();
        count = 4 * N / 15 + 2 * 2 * N / 5;
        System.out.println(count);
    }
}