import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws FileNotFoundException {
		new Main().run();
	}

	final long MODULO = 1_000_000_000 + 7;

	void run() {
		Scanner sc = new Scanner(System.in);
		int w = sc.nextInt();
		int h = sc.nextInt();
		int m = Math.min(w, h);
		int M = Math.max(w, h);
		System.out.println(f(m, M));
	}

	long f(int m, int M) {
		if (m > M) {
			int d = M;
			M = m;
			m = d;
		}
		if (m == 0 && M == 0) {
			return 0;
		}
		if (m == 0 && M > 0) {
			return 1;
		}
		if (m == 1) {
			return 2 * M + 1;
		}
		return 2 * (m + M - 1) + f(m - 2, M - 2);
	}

	void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}
}