import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        // 整数の入力
        int n = sc.nextInt();
      int l = sc.nextInt();
      int res=0;
      if(l>0){
        res=(2*l+n)*(n-1)/2;
      }else if(l+n-1<0){
        res=(2*l+n-2)*(n-1)/2;
      }else{
        res=(2*l+n-1)*n/2;
      }
        System.out.println(res);
    }

}

/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