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 ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    }
} 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 ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int l = sc.nextInt();
        int ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    } main {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int l = sc.nextInt();
        int ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    } 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 ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1); ans n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1) n * (n + 1) / 2 + n * (l - 1) n * (n + 1) / 2 n * (n + 1) n (n + 1) n 1 2 n * (l - 1) n (l - 1) l 1 (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1) l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) l (l > 0 ? 1 : (n > -l ? -l + 1 : n)) l > 0 l 0 1 (n > -l ? -l + 1 : n) n > -l n -l l -l + 1 -l l 1 n 1 System.out.println(ans) System.out.println System.out System System.out ans 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 ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int l = sc.nextInt();
        int ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    }
} 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 ans = n * (n + 1) / 2 + n * (l - 1)
                - (l + (l > 0 ? 1 : (n > -l ? -l + 1 : n)) - 1);
        System.out.println(ans);
    }
}
