import java.util.Scanner;
//import java.util.*;

public class Main {

	public static void main(String args[]) {
		
		Scanner cin = new Scanner(System.in);
		String str ;
		int m,n,sum,a;
		while(true){
			m = cin.nextInt();
			n = cin.nextInt();
			if(m == 0&&n == 0)
				break;
			sum = 0;
			for(int i = 0;i < m;i++){
				str = cin.next();
				a = cin.nextInt();
				sum += a;
			
			}
			System.out.println(3*n - sum);
		}
		
	
	}

}