#include <cassert>
#include <iostream>
#include <vector>
using namespace std;

#include <atcoder/modint>
using mint = atcoder::modint998244353;

template <typename modint> struct acl_fac {
    std::vector<modint> facs, facinvs;
    acl_fac(int N) {
        assert(-1 <= N and N < modint::mod());
        facs.resize(N + 1, 1);
        for (int i = 1; i <= N; i++) facs[i] = facs[i - 1] * i;
        facinvs.assign(N + 1, facs.back().inv());
        for (int i = N; i > 0; i--) facinvs[i - 1] = facinvs[i] * i;
    }
    modint ncr(int n, int r) const {
        if (n < 0 or r < 0 or n < r) return 0;
        return facs[n] * facinvs[r] * facinvs[n - r];
    }
    modint operator[](int i) const { return facs[i]; }
    modint finv(int i) const { return facinvs[i]; }
};
acl_fac<mint> fac(1000000);


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

    if (X > Y) swap(X, Y);

    int K = Y - X;

    mint ret = 0;

    mint pow2 = 1;  // 2^i
    for (int i = 0; i <= X; ++i) { // i: (# of AA) + (# of BB)
        for (int j = 0; i + j <= X; ++j) {  // j: (# of AB)
            int k = j + K; // k: (# of BA)
            ret += fac.ncr(i + j + k, i) * fac.ncr(j + k, j) * pow2;
        }
        pow2 *= 2;
    }

    cout << ret.val() << '\n';
}