import java.util.Scanner;

public class Leijia{
	public static void main(String[] args){
		int sum = 0;
		Scanner in = new Scanner(System.in);
		System.out.print("计算从m到n的和\n");
		System.out.print("请输入m的值\n");
		int m = in.nextInt();
		System.out.print("请输入n的值\n");
		int n = in.nextInt();
		while(m<=n)
		{
			sum = sum + m;
			m++;			
		}
		System.out.println(sum);  	
						
	}
		
}