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 c = 0;
		int d = 1;
		int x = 0;
		boolean v = true;
		int e[] = new int[n];
		for (int i = 0; n > i; i++) {
			c = l + d -1;
			d = d+1;
			e[i] = c;
			x = x + c;
			if(c == 0) {
				v  = false;
			}
		}
		if(v == false) {
			System.out.println(x);
		}else {
			if(l >= 0) {
				System.out.println(x - e[0]);
			}else {
				System.out.println(x - e[n-1]);
			}
		}
	}
}
/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