#include<bits/stdc++.h>

using namespace std;
using ll = long long int;
using lc = complex<double>;

int main(void) {
    constexpr ll MOD = 1e9 + 7;
    constexpr double PI = acos(-1);
    cout << fixed << setprecision(32);
    cin.tie(0); ios::sync_with_stdio(false);

    ll n, k;
    cin >> n >> k;
    if(n&1) {
        cout << min(k+1, n)/2*2 << endl;;
    } else {
        cout << min(n/2, k*2/2) << endl;
    }
}