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 s =Math.max(1-L,1);
    int t =Math.min(s,N);
    int x =0;
    for(int i=1;i<=N;i++){
      if(i==t){continue;}
      else{x=x+L-1+i;}}
    System.out.println(x);
  }
}
/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