import java.util.*;

class Main {
	  static int mod=1_000_000_007;
  public static void main(String[] args) {
	  Scanner sc = new Scanner(System.in);
      long cnt =0;
      int flg=0;
      long N = sc.nextInt();
      long L = sc.nextInt();
      
      for(int i=0;i<N;i++) {
    	  cnt=cnt+L+i;
    	  if(L+i==0) {
    		  flg = 1;
    	  }
      }
      if (flg==0) {
    	  if(L<0) {
    		  cnt = cnt -(L+N-1);
    	  } else {
    		  cnt = cnt - (L);
    	  }
      }
      
      System.out.println(cnt);    	  
  }
 
}
/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