import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int x=sc.nextInt();
		int sum=0;
		sum=3*x+(n-x)+3*x/2;
System.out.println(sum);
	
sc.close();
}
}
