
import java.util.*;

class Main{
    public static void main(String[] args) {
        Scanner stdIn = new Scanner(System.in);
        int n = stdIn.nextInt();
        int L = stdIn.nextInt();
        int minAbs = 100 + 200 - 1;
        int t = 0;
        if(L <= 0){
            if(L + n - 1 >= 0);
            else t = L + n - 1;
        }else{
            t = L;
        }
        System.out.println( n * (n + 2 * L -1) / 2 - t );
    }
}
/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