#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using mint = modint998244353;

constexpr int FACT_SIZE = 1000000;
mint Fact[FACT_SIZE + 1];
mint iFact[FACT_SIZE + 1];
const auto fact_init = [] {
    Fact[0] = mint::raw(1);
    for(int i = 1; i <= FACT_SIZE; ++i) {
        Fact[i] = Fact[i-1] * i;
    }
    iFact[FACT_SIZE] = Fact[FACT_SIZE].inv();
    for(int i = FACT_SIZE; i; --i) {
        iFact[i-1] = iFact[i] * i;
    }
    return false;
}();

mint comb(int n, int k) {
    if (k == 0) return mint::raw(1);
    assert(n >= 0 && k >= 0);
    if (k > n) return mint::raw(0);
    return Fact[n] * iFact[n - k] * iFact[k];
}

mint icomb(int n, int k) {
    return iFact[n] * Fact[n - k] * Fact[k];
}

mint fact(int n) {return Fact[n];}
mint perm(int n, int k) {
    assert(0 <= n);
    return Fact[n] * iFact[n - k];
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int x, y;
  cin >> x >> y;
  x++; y++;
  if (x > y) swap(x, y);
  vector<mint> d(x), f(2 * x), g(x);
  f[0] = 1;
  for(int i = 1; i < 2 * x; i++) f[i] = f[i - 1] * (y - x + i);
  rep(i, x) g[i] = mint(2).pow(i) / fact(i);
  auto dfs = [&](auto&& self, int l, int r) {
    if (l + 1 == r) {
      d[l] += f[x + l - 1] * g[x - l - 1];
      return;
    }
    int c = (l + r) / 2;
    self(self, l, c);
    self(self, c, r);
    // [l, c) * [x - r, x - c)
    // [2l+x-r,2l+x-c),...,[2(c-1)+x-r,2(c-1)+x-c)
    vector<mint> a(2 * (c - 1) + x - c - (2 * l + x - r)), b((x - c) - (x - r));
    for(int i = 2 * l + x - r; i < 2 * (c - 1) + x - c; i++) a[i - (2 * l + x - r)] = f[i];
    for(int i = x - r; i < x - c; i++) b[i - (x - r)] = g[i];
    reverse(all(b));
    vector<mint> ab = convolution(a, b);
    for(int i = l; i < c; i++) d[i] += ab[2 * i + x - c - 1 - (2 * l + x - r)];
  };
  dfs(dfs, 0, x);
  mint ans;
  rep(i, x) ans += d[i] / (fact(i) * f[i]);
  cout << ans.val() << endl;
}