import java.util.*;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] array1 = new int[n];
    int[] array2 = new int[n];
    int l = sc.nextInt();
    int sum = 0;
    for(int i=0; i<n; i++){
      array1[i] = l + i;
    }
    if(array1[0]>0){
      for(int i=1; i<n; i++){
        sum += array1[i];
      }
    }else if(array1[n-1]<0){
      for(int i=0; i<n-1; i++){
        sum += array1[i];
      }
    }else{
      for(int i=0; i<n; i++){
        sum += array1[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