import java.util.*;
public class Main{
  public static void main(String[]args){
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


}
} import java.util.*; util.* java public class Main{
  public static void main(String[]args){
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


}
} Main public static void main(String[]args){
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


} main {
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int l = sc.nextInt(); l sc.nextInt() sc.nextInt sc int[] data = new int[n]; data new int[n] n int sum = 0; sum 0 for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      } int i = 0; int i = 0; i 0 i<n i n i++ i++ i {
        data[i] = l+i;
        sum += data[i];
      } {
        data[i] = l+i;
        sum += data[i];
      } data[i] = l+i data[i] data i l+i l i sum += data[i] sum data[i] data i if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      } data[n-1]<0 data[n-1] data n-1 n 1 0 {
        System.out.println(sum-data[n-1]);
        System.exit(0);
      } System.out.println(sum-data[n-1]) System.out.println System.out System System.out sum-data[n-1] sum data[n-1] data n-1 n 1 System.exit(0) System.exit System 0 if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      } l>0 l 0 {
        sum -= data[0];
        System.out.println(sum);
      } sum -= data[0] sum data[0] data 0 System.out.println(sum) System.out.println System.out System System.out sum {
        System.out.println(sum);
      } System.out.println(sum) System.out.println System.out System System.out sum String[]args args public class Main{
  public static void main(String[]args){
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


}
} public class Main{
  public static void main(String[]args){
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


}
} Main
import java.util.*;
public class Main{
  public static void main(String[]args){
      Scanner sc = new Scanner(System.in);

      int n = sc.nextInt();
      int l = sc.nextInt();
      int[] data = new int[n];
      int sum = 0;
      for (int i = 0;i<n ;i++ ) {
        data[i] = l+i;
        sum += data[i];
      }

      if(data[n-1]<0){
        System.out.println(sum-data[n-1]);
        System.exit(0);
      }

      if(l>0){
        sum -= data[0];
        System.out.println(sum);
      }else{
        System.out.println(sum);
      }


}
}
