import java.util.Scanner;

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

		if (n % 2 == 0) {
			int ans = n / 2;
			int k1 = 1 + k;
			int k2 = n + 1 - k;
			if (k1 < k2) {
				ans -= (k2 - k1) / 2 - 1;
			}
			System.out.println(ans);
		} else {
			System.out.println(Math.min(n, k + 1));
		}
	}
}