//  E - Distance on Large Perfect Binary Tree

#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ld long double
#define ar array
#define fi first
#define se second
#define ii pair <int, int>
#define vt vector
#define pb push_back
#define sz(x) (int)(x).size()
#define reset(a, x) memset(a, x, sizeof(a))
#define END cerr << "\n";
#define endl "\n"

#define error(args...) { \
	string _s = #args; \
	replace(_s.begin(), _s.end(), ',', ' '); \
	stringstream _ss(_s); \
	istream_iterator <string> _it(_ss); \
	err(_it, args); \
}

void err(istream_iterator<string> it) {}

template<typename T, typename... Args> 
void err(istream_iterator<string> it, T a, Args... args) {
	cerr << *it << "=" << a << ", ";
	err(++it, args...);
}

template<class T> void read(T& x) {
	cin >> x;
}

template<class H, class... T> void read(H& h, T&... t) {
	read(h);
	read(t...);
}

template<class A> void write(A x) {
	cout << x;
}

template<class H, class... T> void write(const H& h, const T&... t) { 
	write(h);
	write(t...);
}

void print() {
	write("\n");
}

template<class H, class... T> void print(const H& h, const T&... t) { 
	write(h);
	if(sizeof...(t))
		write(' ');
	print(t...);
}

#define file ""

inline void setIO() {
	//freopen(file".out", "w", stdout); freopen(file".in", "r", stdin);
	cin.tie(0)->sync_with_stdio(0);
}

const long long INF = 2e18;
const int inf = 0x3c3c3c3c, N = 1e6, D = 2e6+1, mod = 998244353;
int n, d, pow2[D], dp[D];

int mul(int a, int b) {
	return (1ll * a * b) % mod;
}

int add(int a, int b) {
	a += b;
	if (a >= mod) a -= mod;
	return a;
}

void solve() {
	read(n, d);
	pow2[0] = 1;
	for (int i = 1; i <= d; i++) pow2[i] = mul(pow2[i-1], 2);
	int lim = (d % 2 ? (d + 1) / 2 : d / 2);
	for (int i = lim; i < d; i++) {
		dp[i] = mul(pow2[i-1], pow2[d-i-1]);
		dp[i] = mul(dp[i], 2);
		dp[i] = add(dp[i], dp[i-1]);
	}
	//error(dp[1]);
	int ans = 0;
	for (int i = 0; i < n; i++) {
		int curAns = (i + d < n ? mul(pow2[d], 2) : 0);
		int curLim = min(d-1, n-i-1);
		if (curLim < lim) break;
		curAns = add(curAns, dp[curLim]);
		curAns = mul(curAns, pow2[i]);
		ans = add(curAns, ans);
		//cerr << ans << endl;
	}
	write(ans);
}

int32_t main() {
	setIO();
	int Case = 1;
	//read(Case);
	for (int ttest = 1; ttest <= Case; ttest++) {
		//write("Case ", ttest, ": ");
		solve();
	}
}