import java.util.Scanner;

public class Main {

	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = Integer.parseInt(sc.next());
		int l = Integer.parseInt(sc.next());
		int sum = 0;
		for (int i = 1; i <= n; i++) {
			sum += l + i - 1;
		}
		int ans = 0;
		for (int i = 1; i <= n; i++) {
			if (Math.abs(sum - ans) > Math.abs(l + i - 1)) {
				ans = sum - (l + i - 1);
			}
		}
		System.out.println(ans);
		sc.close();
	}
}
/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