import java.util.*;
public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		// 文字列の入力
		int N = sc.nextInt();
      	int L = sc.nextInt();
      	int aji[] = new int[N];
      	int sum = 0;
      	int min = L;
		
      	for(int i=1;i<=N;i++){
          aji[i-1] = L + i - 1;
          if(Math.abs(aji[i-1]) < Math.abs(min)){
            min = aji[i-1];
          }
          sum = sum + aji[i-1];
        }
      System.out.println(sum-min);
	}
}
/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