import java.util.*;

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

        int n = in.nextInt();
        int m = in.nextInt();

        int even = 0;
        int odd = 0;
        for (int i = 0; i < n ; i++) {
            even += i;
        }
        for (int i = 0; i < m ; i++) {
            odd += i;
        }

        System.out.println(even+odd);
    }
}
/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