import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
      Scanner in = new Scanner(System.in);
      int n = in.nextInt(), m = in.nextInt();
      int ans = (n*n-n+m*m-m)/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