import java.util.Scanner;

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*N-N+(1+N)*N/2;
		int absMin = Math.abs(L);
		int bite = L;
		for (int i=2;i<=N;i++) {
			if (Math.abs(L+i-1)<absMin) {
				absMin = Math.abs(L+i-1);
				bite = L+i-1;
			}
		}
		System.out.println(sum-bite);
	}
}
/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