import java.util.*;

public class Main{
	public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	}
} import java.util.*; util.* java public class Main{
	public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	}
} Main public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	} main {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int L = sc.nextInt(); L sc.nextInt() sc.nextInt sc sc.close() sc.close sc int result = (N *(2 * L + N - 1))/2; result (N *(2 * L + N - 1))/2 (N *(2 * L + N - 1)) N (2 * L + N - 1) 2 * L + N 2 * L 2 L N 1 2 result -= ((L >= 0)?L:Math.min(0, L + N - 1)) result ((L >= 0)?L:Math.min(0, L + N - 1)) (L >= 0) L 0 L Math.min(0, L + N - 1) Math.min Math 0 L + N - 1 L + N L N 1 System.out.println(result) System.out.println System.out System System.out result String args[] args public class Main{
	public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	}
} public class Main{
	public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	}
} Main
import java.util.*;

public class Main{
	public static void main(String args[]) {

		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int L = sc.nextInt();
		sc.close();
		
		int result = (N *(2 * L + N - 1))/2;
		result -= ((L >= 0)?L:Math.min(0, L + N - 1));
		
		System.out.println(result);
	}
}