#include<iostream>
using namespace std;

int main() {
	int n, k;
	cin >> n >> k;
	int ans;
	if (k == 0 || k > n)ans = n;
	else if (k == (n + 1) / 2 && n & 1)ans = 1;
	else ans = 2;
	cout << n-ans << endl;
}