import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int l = sc.nextInt();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  }
} import java.util.Scanner; Scanner 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();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  }
} Main public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int l = sc.nextInt();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  } main {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int l = sc.nextInt();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  } 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 int appleToRemove = Math.max(1, Math.min(n, -l + 1)); appleToRemove Math.max(1, Math.min(n, -l + 1)) Math.max Math 1 Math.min(n, -l + 1) Math.min Math n -l + 1 -l l 1 System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1)) System.out.println System.out System System.out (2 * l + n - 1) * n / 2 - (l + appleToRemove - 1) (2 * l + n - 1) * n / 2 (2 * l + n - 1) * n (2 * l + n - 1) 2 * l + n 2 * l 2 l n 1 n 2 (l + appleToRemove - 1) l + appleToRemove l appleToRemove 1 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();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  }
} public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int l = sc.nextInt();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  }
} Main
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int l = sc.nextInt();

    int appleToRemove = Math.max(1, Math.min(n, -l + 1));

    System.out.println((2 * l + n - 1) * n / 2 - (l + appleToRemove - 1));
  }
}