// what is matter? never mind. 
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
//#pragma GCC target("sse,sse2,sse3,sse4,popcnt,abm,mmx,avx,avx2") 
#include<bits/stdc++.h>
#define For(i,a,b) for(int i=(a);i<=(b);++i)
#define Rep(i,a,b) for(int i=(a);i>=(b);--i)
#define ll long long
#define ull unsigned long long
using namespace std;
inline int read()
{
	char c=getchar();int x=0;bool f=0;
	for(;!isdigit(c);c=getchar())f^=!(c^45);
	for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
	if(f)x=-x;return x;
}
 
#define mod 998244353
struct modint{
	int x;
	modint(int o=0){x=o;}
	modint &operator = (int o){return x=o,*this;}
	modint &operator +=(modint o){return x=x+o.x>=mod?x+o.x-mod:x+o.x,*this;}
	modint &operator -=(modint o){return x=x-o.x<0?x-o.x+mod:x-o.x,*this;}
	modint &operator *=(modint o){return x=1ll*x*o.x%mod,*this;}
	modint &operator ^=(int b){
		modint a=*this,c=1;
		for(;b;b>>=1,a*=a)if(b&1)c*=a;
		return x=c.x,*this;
	}
	modint &operator /=(modint o){return *this *=o^=mod-2;}
	friend modint operator +(modint a,modint b){return a+=b;}
	friend modint operator -(modint a,modint b){return a-=b;}
	friend modint operator *(modint a,modint b){return a*=b;}
	friend modint operator /(modint a,modint b){return a/=b;}
	friend modint operator ^(modint a,int b){return a^=b;}
	friend bool operator ==(modint a,int b){return a.x==b;}
	friend bool operator !=(modint a,int b){return a.x!=b;}
	bool operator ! () {return !x;}
	modint operator - () {return x?mod-x:0;}
	bool operator <(const modint&b)const{return x<b.x;}
};
inline modint qpow(modint x,int y){return x^y;}

vector<modint> fac,ifac,iv;
inline void initC(int n)
{
	if(iv.empty())fac=ifac=iv=vector<modint>(2,1);
	int m=iv.size(); ++n;
	if(m>=n)return;
	iv.resize(n),fac.resize(n),ifac.resize(n);
	For(i,m,n-1){
		iv[i]=iv[mod%i]*(mod-mod/i);
		fac[i]=fac[i-1]*i,ifac[i]=ifac[i-1]*iv[i];
	}
}
inline modint C(int n,int m){
	if(m<0||n<m)return 0;
	return initC(n),fac[n]*ifac[m]*ifac[n-m];
}
inline modint sign(int n){return (n&1)?(mod-1):(1);}

#define fi first
#define se second
#define pb push_back
#define mkp make_pair
typedef pair<int,int>pii;
typedef vector<int>vi;

#define maxn 1000005
#define inf 0x3f3f3f3f

int n,d;
modint res[maxn];

modint C2(int n,int m){
	return C(n+m-1,m-1);
}
modint F(int n,int d){
	if(n<d)return 0;
	return C((n+d)/2,d);
}

modint sum[maxn];
modint tmp[maxn];

signed main()
{
	n=read(),d=read();
	For(i,0,n){
	//	cout<<"i: "<<i<<"\n";
		for(int j=i-1;j>=0;j-=2) res[i]+=res[j];
	//	For(k,0,d)cout<<F(i,k).x<<" ";cout<<"\n";
		For(k,0,d) res[i]+=F(i,k)*F(i,d-k);
		For(k,0,d-2) sum[i]+=F(i,k)*F(i,d-2-k);
		sum[i]+=sum[i-2];
		res[i]-=sum[i-1];
//		cout<<"res "<<res[i].x<<"\n";
//		for(int j=i-1;j>=0;j-=2){
//			For(k,0,d-2)
//				res[i]-=F(j,k)*F(j,d-2-k);
//		}
	//	cout<<"res "<<res[i].x<<"\n";
//		For(k,0,d)cout<<tmp[k].x<<" "<<F(i,k).x<<"\n";
//		For(k,0,d)assert(tmp[k].x==F(i,k).x);
//		cout<<"res "<<res[i].x<<"\n";
	}
	res[n]*=((mod+1)/2);
	cout<<res[n].x;
	return 0;
}
/*

*/