백준 #8760번 Schronisko

import java.util.Scanner;
public class Main {
	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		int n = sc.nextInt();
		for(int i = 0; i < n; i++) {
			int a = sc.nextInt();
			int b = sc.nextInt();
			System.out.println(a * b / 2);
		}
		sc.close();
	}
}