import java.util.*;
import java.io.*;
public class Main {
  public static void main(String[] args) throws Exception {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int M = sc.nextInt();
    int resultEven =0;
    int resultOdd=0;
    if(N>1){
      resultEven=nCr(N,2);
    }
    if(M>1){
      resultOdd=nCr(M,2);
    }
    
    int result=resultEven+resultOdd;
    
    
    System.out.println(result);
  }
  static int nCr(int n, int r) 
{ 
    return (n*(n-1))/2;
} 
  
// Returns factorial of 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