import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    }
} import java.util.*; util.* java public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    }
} Main public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    } main {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n n m m ans; ans n = sc.nextInt() n sc.nextInt() sc.nextInt sc m = sc.nextInt() m sc.nextInt() sc.nextInt sc ans = ((n + m) * (n + m - 1)) / 2 - (n * m) ans ((n + m) * (n + m - 1)) / 2 - (n * m) ((n + m) * (n + m - 1)) / 2 ((n + m) * (n + m - 1)) (n + m) n m (n + m - 1) n + m n m 1 2 (n * m) n m System.out.println(ans) System.out.println System.out System System.out ans String[] args args public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    }
} public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    }
} Main
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        int n,m,ans;
        
        n = sc.nextInt();
        m = sc.nextInt();
        
        
        ans = ((n + m) * (n + m - 1)) / 2 - (n * m);
        
        
        System.out.println(ans);
    }
}
