sum

package mainscond;



import java.util.Scanner;

public class sum {


	public int getSum(int begin,int end) {
		int sum=0;
		while(begin<=end) {
			sum=sum+begin++;
		}
		return sum=sum+end;

	}

	public static void main(String[] args) {
		sum s =new sum();
		Scanner sc=new Scanner(System.in );
		int begin=sc.nextInt();
		Scanner sc1=new Scanner(System.in );
		int end=sc.nextInt();
		// TODO Auto-generated method stub
		System.out.print(s.getSum(begin, end));

	}


}