#include <atcoder/modint>
#include <cassert>
#include <iostream>
#include <vector>
using namespace std;

template <int md> std::istream &operator>>(std::istream &is, atcoder::static_modint<md> &x) {
    long long t;
    return is >> t, x = t, is;
}
template <int md> std::ostream &operator<<(std::ostream &os, const atcoder::static_modint<md> &x) { return os << x.val(); }

using mint = atcoder::modint998244353;

int main() {
    int X, Y;
    cin >> X >> Y;

    vector dp(X + 1, vector<mint>(Y + 1)); // dp[x][y]: 最小で AB x 個 BA y 個で作れる列の個数
    dp[0][0] = 1;

    mint ret = 0;

    for (int i = 0; i < int(dp.size()); ++i) {
        for (int j = 0; j < int(dp[i].size()); ++j) {
            // AA 始まり / BB 始まり
            if (i and j) dp[i][j] += dp[i - 1][j - 1] * 2;

            // AB 始まり
            if (i) dp[i][j] += dp[i - 1][j];

            // BA 始まり
            if (j) dp[i][j] += dp[i][j - 1];

            if (j - i == Y - X) ret += dp[i][j];
        }
    }
    cout << ret.val() << '\n';
}