import java.util.*;
import static java.lang.Math.*;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	}
} import java.util.*; util.* java import static java.lang.Math.*; import static java.lang.Math.*; import static java.lang.Math.*; import java.math.BigInteger; BigInteger java.math public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	} main {
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	} 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 result = 0; result 0 int skip = 0; skip 0 if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		} l >= 0 l 0 {
		    skip = 1;
		} skip = 1 skip 1 if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		} l + n - 1 <= 0 l + n - 1 l + n l n 1 0 {
		    skip = n;
		} skip = n skip n {
		    skip = 0;
		} skip = 0 skip 0 for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		} int i = 1; int i = 1; i 1 i <= n i n i++ i++ i {
		    if(i == skip) continue;
		    result += l + i - 1;
		} {
		    if(i == skip) continue;
		    result += l + i - 1;
		} if(i == skip) continue; i == skip i skip continue; result += l + i - 1 result l + i - 1 l + i l i 1 System.out.println(result) System.out.println System.out System System.out result String[] args args public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	}
} public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	}
} Main
import java.util.*;
import static java.lang.Math.*;
import java.math.BigInteger;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		// 入力
		int n = sc.nextInt();
		int l = sc.nextInt();
		
		// 計算
		int result = 0;
		int skip = 0;
		if(l >= 0){
		    skip = 1;
		}else if(l + n - 1 <= 0 ){
		    skip = n;
		}else{
		    skip = 0;
		}
		for(int i = 1; i <= n; i++){
		    if(i == skip) continue;
		    result += l + i - 1;
		}

		// 出力
		System.out.println(result);
		
	}
}
