import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextInt();
		long m = sc.nextInt();
		sc.close();

		if (n == 1) {
			System.out.println(0);
		} else if (n % 2 == 0) {
			System.out.println(n * m);
		} else {
			long v1 = (n - 3) * m;
			long v2 = 0;
			int cnt = 0;
			for (int i = 30; i >= 0; i--) {
				if ((m >> i & 1) == 1) {
					cnt++;
					v2 += 1L << i;
				} else if (cnt >= 2) {
					v2 += 1L << i;
				}
			}
			System.out.println(v1 + v2 * 2);
		}
	}
}