$TLE$ $at$ $6$

#include<bits/stdc++.h>
#define int long long 

const int N=35;

using namespace std;

int n,m;
int f[N][N];

int dfs(int x,int num){
	if(min(abs(x-1),abs(n-x+1))>m-num) return 0;
	if(x==1 && num==m) return 1;
	if(num==m) return 0;
	if(f[x][num]) return f[x][num];
	int res=0,l,r;
	if(x+1>n) l=1;
	else l=x+1;
	if(x-1==0) r=n;
	else r=x-1;
	res+=dfs(l,num+1)+dfs(r,num+1);
	f[x][num]=res;
	return res;
}

signed main(){
	cin>>n>>m;
	else cout<<dfs(1,0)<<endl;
	return 0;
}