#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    ll n, k;
    cin >> n >> k;
    ll ans = 0;
    rep(bit, 1LL << n) {
        set<ll> left, right;
        rep(i, n) {
            if ((bit & (1LL << i)) != 0) left.insert(i + 1);
            else right.insert(i + 1);
        }
        if ((sz(left) == 0) || (sz(right) == 0)) continue;
        ll lmin = *left.begin(), lmax = *left.rbegin();
        ll rmin = *right.begin();
        if (lmin != k) continue;
        if (lmax < rmin) continue;
        ans++;
    }
    cout << ans << endl;
    return 0;
}