Untitled

import java.util.Scanner;

public class sahil2 {
    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        int u = sc.nextInt();
        int v = sc.nextInt();

        int e, e1, o, o1;

        e = u / 2;
        o = u / 2;
        o1 = v / 2;
        e1 = v / 2;

        if (u % 2 != 0)
            o++;

        if (v % 2 != 0)
            o1++;

        System.out.println(e * e1 + o * o1);

    }

}