// No.1771 A DELETEQ
#include <bits/stdc++.h>

using namespace std;

#define	MOD	998244353

int main(int argc, char *argv[])
{
	auto mpow = [&](long long x, long long n) {
		long long r = 1;
		for ( ; n > 0; x = x * x % MOD, n >>= 1) if (n & 1) r = r * x % MOD;
		return r;
	};

	long long x, y;
	cin >> x >> y;
	if (x > y) swap(x, y);
	vector<long long> p(x + 1, 1);
	for (int i = 1; i <= x; i++) p[i] = p[i - 1] * 2 % MOD;
	long long ans = 0;
	for (int k = 0; k <= x; k++) {
		long long n = x + y - k - k, t = 1, r = 1, m = 1;
		for (int j = 0; j < x - k; j++)
			m = m * (n - j) % MOD * mpow(j + 1, MOD - 2) % MOD;
		for (int j = 1; j <= k; j++) {
			t = t * (n + j) % MOD * mpow(j, MOD - 2) % MOD;
			r = (r + t * p[j] % MOD) % MOD;
		}
		ans = (ans + r * m % MOD) % MOD;
	}

	cout << ans << endl;

	return 0;
}