#include<iostream>
using namespace std;
long long dp[1<<20][20][2];
int main(){
	int n,m;cin>>n>>m;m--;dp[1<<m][m][0]=1;
	for(int i=0;i<(1<<n);i++){
		for(int j=0;j<n;j++){
			if(dp[i][j][0]+dp[i][j][1]==0)continue;
			for(int k=0;k<n;k++){
				if((i/(1<<k))%2==1)continue;
				if(j>k)dp[i+(1<<k)][k][1]+=dp[i][j][0];
				else{
					dp[i+(1<<k)][k][0]+=dp[i][j][0];
					dp[i+(1<<k)][k][1]+=dp[i][j][1];
				}
			}
		}
	}
	long long sum=0;
	for(int i=0;i<n;i++)sum+=dp[(1<<n)-1][i][1];
	cout<<sum<<endl;
	return 0;
}