import java.util.*;
class Main{
    public static void main(String[] args){
	Scanner stdIn = new Scanner(System.in);
        int N = stdIn.nextInt();
	int M = stdIn.nextInt();
	int m=(M*(M-1))/2; //偶数を２つ選ぶ
	int n=(N*(N-1))/2; //奇数を２つ選ぶ
	System.out.println(m+n);
    }
}
	    
	    

/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