#include<bits/stdc++.h>
using namespace std;

int main() {
    int N, K; cin >> N >> K;
    int x = 0;
    if (K<1 || K>N) x = N;
    else if (N == K * 2 - 1) x = 1;
    else x = 2;

    cout << (N - x) << endl;

    return 0;
}