import java.util.Scanner;

class Main 
{

	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in);
		
		int evenBalls = sc.nextInt();
		
		int oddBalls  = sc.nextInt();
		
		
		
		int evenAvailable = 0;
		
		for(int i=1; i<evenBalls; i++)
		{
			evenAvailable += i;
			
		}
		
		
		for(int i=1; i<oddBalls; i++)
		{
			evenAvailable += i;
			
		}
		
		System.out.println(evenAvailable);
		
		
		

	}

}

/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