import java.util.Scanner;
public class Main
{
 	public static void main(String[] args)
    {
     	 Scanner sc = new Scanner(System.in);
      	String[] sep = sc.nextLine().split(" ");
      	int n = Integer.parseInt(sep[0]); 
  		int m = Integer.parseInt(sep[1]);
  		System.out.println( n * (n - 1) / 2 + m * (m - 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