#include <algorithm>
#include <iostream>
#include <vector>

int main() {
    using namespace std;
    int n, k;
    cin >> n >> k;
    k--;
    int ans = 0;
    for (int bit = 0; bit < (1 << n); bit++) {
        int a_min = n, a_max = 0, b_min = n;
        for (int i = 0; i < n; i++) {
            if (bit >> i & 1) {
                a_min = min(a_min, i);
                a_max = max(a_max, i);
            } else {
                b_min = min(b_min, i);
            }
        }
        if (a_min == n || b_min == n) { continue; }
        if (a_min == k && a_max > b_min) { ans++; }
    }
    cout << ans << endl;
}