import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int evenBalls = sc.nextInt();
        int oddBalls = sc.nextInt();
	    int result = execute(evenBalls,oddBalls);
        System.out.println(result);
    }

    public static int execute(int evenBalls, int oddBalls){
        //偶数と偶数、奇数と奇数でのみ組み合わせ
        return evenBalls*(evenBalls - 1)/2
                +oddBalls*(oddBalls - 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