import java.util.Scanner;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();
        in.close();
        int numOfMinCut = findMinCut(n,m);
        System.out.println(numOfMinCut);
    }

	private static int findMinCut(int n, int m) {
		if ( n == 1 && m == 1) return 0;
		else if(n == 1 && m > 1) return m-1;
		else if( n > 1 && m == 1) return n-1;
		else {
			int cutV = 1 + findMinCut(n, 1) + findMinCut(n, m-1);
			int cutH = 1 + findMinCut(1, m) +findMinCut(n-1, m);
			
			return Math.min(cutV, cutH);
		}
		
	}
}