import java.util.*;
public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = Integer.parseInt(sc.next());
    int l = Integer.parseInt(sc.next());

    if(l<0 && n+l-1<0){
      System.out.println((2*l+n-2)*(n-1)/2);
    }else if(l>0){
      System.out.println((2*l+n)*(n-1)/2);
    }else{
      System.out.println((2*l+n-1)*n/2);
    }

  }
}
/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