import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        
        Scanner sc = new Scanner(System.in);
        long n = sc.nextLong();
        long m = sc.nextLong();
        
        long cut = 0;
        if (n >= m){
            
        }
        
        long cut1 = Math.max(0, Math.min(m-1,n-1));
        long cut2 = Math.max(0, Math.max(m-1,n-1) * (cut1+1));
        System.out.println(cut1+cut2);
    }
}