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 Sum = l;
    
    if(l>=0){
      Sum = 0;
      for(int i=1;i<n;i++){
        Sum += l+i;
      }
    }else{
      if(n+l > 0){
        for(int i=1;i<n;i++){
          Sum += l+i;
        }
      }else{
        for(int i=1;i<n-1;i++){
        	Sum += l+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