import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int even = sc.nextInt();
		int odd = sc.nextInt();
		//奇数+奇数か偶数+偶数しかありえない
		if(even == 0) {
			System.out.println(odd*(odd-1)/2);
			return;
		}
		if(odd == 0) {
			System.out.println(even*(even-1)/2);
			return;
		}
		
		System.out.println( odd*(odd-1)/2 + even*(even-1)/2);
		
	}
		
}
/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