import java.util.Scanner;

public class Main {
    public static void main(String[] argv) {
        Scanner scanner = new Scanner(System.in);

        String line = scanner.nextLine();

        String[] mn = line.split(" ");
        int m = Integer.parseInt(mn[0]);
        int n = Integer.parseInt(mn[1]);

        int ans = m  * (m - 1) / 2  + n * (n - 1) / 2;

        System.out.println(ans);

    }
}

/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