#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

int main(){
    int N, K;
    cin >> N >> K;
    K--;
    int ans = 0;
    FOR(S, 1, (1<<N)-1){
        bool ok = true;
        rep(i, K)if(S >> i & 1)ok = false;
        ok &= S >> K & 1;
        if(!ok)continue;
        int x = -1, y = INT_MAX;
        for(int i = N - 1; i >= 0; --i)if(S >> i & 1){
            x = i; break;
        }
        rep(i, N)if(!(S >> i & 1)){
            y = i; break;
        }
        if(x > y){
            ans++;
        }
    }
    cout << ans << endl;
}