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 ans=0;
		if(0<=L){ans=(2*L+N)*(N-1)/2;}
		if(0>=L+N-1){ans=(2*L+N-2)*(N-1)/2;}
		if(L<= 0 &&  0<=L+N-1){ans=(2*L+N-1)*(N)/2;}
		
		System.out.println(ans);

	
	}
}
/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