import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = Integer.parseInt(sc.next());
		int L = Integer.parseInt(sc.next());
		int[] Eval = new int[N];
		int sum = 0;
		for(int i = 0;i < N;i++) {
			Eval[i] = L+ i;
			sum += Eval[i];
		}
		sc.close();
		int num = 0;
		if(Eval[0] > 0) {
			num = Eval[0];
		}else if(Eval[N-1] < 0) {
			num = Eval[N-1];
		}else {
			num = 0;
		}
		System.out.println(sum - num);
	}
}
/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