import java.io.*;
 
public class Main {
 
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String line = br.readLine();
		String[] info = line.split(" ");
		int N = Integer.parseInt(info[0]);
		int M = Integer.parseInt(info[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