import java.util.*;
import java.io.*;
class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
		
		long n  =sc.nextLong();
		long m = sc.nextLong();
		long a1 = ((n)*(n-1))/2;
		long a2 = ((m)*(m-1))/2;
		System.out.println(a1+a2);
	}
}
/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