
import java.util.Scanner;

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

        if(L>=0){
            int sum=0;
            for(int i=L,j=1;j<=n;i++,j++){
                sum+=i;
            }

            sum-=L;
            System.out.println(sum);
        }
        else{
            int sum=0;
            if(Math.abs(L)>=n){
                for(int i=L,j=1;j<n;i++,j++){
                    sum+=i;
                }
                System.out.println(sum);
            }
            else {
                for(int i=L,j=1;j<=n;i++,j++){
                    sum+=i;
                }
                System.out.println(sum);
            }
        }
    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz