#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;

ll dp[1 << 20][20][2];

int main(){
    int N, K;
    cin >> N >> K;
    dp[1 << (K - 1)][K - 1][0] = 1;
    FOR(mask, 1, 1 << N)rep(pre, N)rep(rev, 2)if(dp[mask][pre][rev]){
        ll val = dp[mask][pre][rev];
        rep(i, N)if(!(mask >> i & 1)){
            if(pre < i)dp[1 << i | mask][i][rev] += val;
            else if(!rev)dp[1 << i | mask][i][1] += val;
        }
    }
    ll ans = 0;
    rep(last, N)ans += dp[(1 << N) - 1][last][1];
    cout << ans << endl;
}