// Validator
#include "testlib.h"
#include <iostream>
#include <utility>
#include <vector>
using namespace std;

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

int main(int argc, char *argv[]) {
    registerValidation(argc, argv);
    int X = inf.readInt(1, 4000);
    inf.readSpace();
    int Y = inf.readInt(1, 4000);
    inf.readEoln();
    inf.readEof();

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

    int K = Y - X;

    mint ret = 0;

    vector<mint> fac(X + Y + 1, 1), facinv = fac;
    for (int i = 1; i < int(fac.size()); ++i) fac[i] = fac[i - 1] * i;
    facinv.back() = fac.back().inv();
    for (int i = int(facinv.size()) - 1; i; --i) facinv[i - 1] = facinv[i] * i;

    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[i + j + k] * facinv[i] * facinv[j] * facinv[k] * pow2;
        }
        pow2 *= 2;
    }

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