[CodeForces][JAVA] 50A - Domino piling

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;
 
 
public class Solution {
        
    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
    
    public static void main(String[] args) throws IOException{
        StringTokenizer stk = new StringTokenizer(br.readLine()," ");
        int extent = Integer.parseInt(stk.nextToken())*Integer.parseInt(stk.nextToken());
        
        bw.write(String.valueOf(extent/2));
        bw.flush();
    }
}