import java.io.*;
import java.util.*;

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. */
        int i,j,m,n,su=0;
        Scanner s=new Scanner(System.in);
        m=s.nextInt();
        n=s.nextInt();
        for(i=n;i>1;i--)
            {
            su=su+1;
        }
        for(i=n;i>0;i--)
            {
            for(j=m;j>1;j--)
                {
                su=su+1;
            }
        }
    System.out.println(su);
    }
}