import java.util.*;

public class Main {
    public static void main(final String[] args) {
        final Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        int M = sc.nextInt();
        sc.close();

        int sum = 0;
        for (int i = 1; i < N; i++) {
            sum += i;
        }
        for (int i = 1; i < M; i++) {
            sum += i;
        }
        System.out.println(sum);
    }
}
/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