#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-12;

int main() {
	int n, k;
	cin >> n >> k;
	
	int ans = 0;
	
	REP(i, 1<<n) {
		vector<int> a, b;
		REP(j, n) {
			if (i >> j & 1) a.push_back(j + 1);
			else b.push_back(j + 1);
		}
		
		if (a.empty() || b.empty()) continue;
		
		if (a.front() != k) continue;
		if (a.back() < b.front()) continue;
		
		ans++;
	}
	cout << ans << endl;
	return 0;
}