//package ro.stancalau;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * Created by Sorin on 4/29/2017.
 */
public class prog {

    long[] predef = new long[1000000000];

    public static void main(final String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
//        for (int n = 1; n <= nn; n++) {
            long l = n;
            l = n + (n / 3L);
            if (n > 3) {
                long start = 0;
                for (int k = n + 1; k <= l; k++) {
                    if (k % 3 == 0) {
                        start = k;
                        break;
                    }
                }
                long stop = 0;
                for (long k = l; k >= n + 1; k--) {
                    if (k % 3 == 0) {
                        stop = k;
                        break;
                    }
                }
                l = l + (stop / 3) - (start / 3) + 1 ;
            }
//            System.out.println(l + "-" + n);
//        }

     System.out.println(l * 3L);
    }
}