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();
        int res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        }
    } 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();
        int res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        }
    } Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int L = sc.nextInt();
        int res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        } main {
		Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int L = sc.nextInt();
        int res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        } 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 res=0; res 0 if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        } L>=0 L 0 {
            res = (N+2*L)*(N-1)/2;
        } res = (N+2*L)*(N-1)/2 res (N+2*L)*(N-1)/2 (N+2*L)*(N-1) (N+2*L) N 2*L 2 L (N-1) N 1 2 if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        } L+N-1>=0 L+N-1 L+N L N 1 0 {
            res = N*(2*L+N-1)/2;
        } res = N*(2*L+N-1)/2 res 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 {
            res = N*(2*L+N-1)/2 - (L+N-1);
        } res = N*(2*L+N-1)/2 - (L+N-1) res N*(2*L+N-1)/2 - (L+N-1) 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 (L+N-1) L+N L N 1 System.out.println(res) System.out.println System.out System System.out res 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 res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        }
    } public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int L = sc.nextInt();
        int res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        }
    } 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();
        int res=0;
        if(L>=0){
            res = (N+2*L)*(N-1)/2;
        }else if(L+N-1>=0){
            res = N*(2*L+N-1)/2;
        }else{
            res = N*(2*L+N-1)/2 - (L+N-1);
        }
        
        System.out.println(res);
        
        }
    }