import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        //每次电梯乘坐12人,第i+1次是小乐该坐的趟次
        int i = n / 12;
        int j = n % 12;
        //如果 j == 0,则第i次是小乐该坐的趟次
        
        if(j == 0 && n != 0) {
            System.out.println(i * 4 - 2);
        } else if(j != 0 && n != 0){
            System.out.println((i + 1) * 4 - 2);
        } else if(n == 0) {
            System.out.println(2);
        }
    }
}