#include <iostream>
#include <vector>
#include <algorithm>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using mint = modint998244353;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vmi = vector<mint>;
using vvmi = vector<vmi>;
using vvvmi = vector<vvmi>;
#define all(a) (a).begin(), (a).end()
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)

int main(){
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    ll h, w; cin >> h >> w;
    if(h == 1 || w == 1){
        cout << 1 << endl;
        return 0;
    }
    vmi kaijo(1000000);
    kaijo[0] = kaijo[1] = mint(1);
    rep2(i, 2, 1000000)kaijo[i] = kaijo[i-1]*mint(i);
    int right = 1, down = 1;
    int dummy = 0;
    mint ans = mint(0);
    while(right <= w && down <= h-1){
        ll free = h*w - (h+w-1+dummy);
        int rfree = w - right;
        mint r = kaijo[rfree+right-1]/(kaijo[rfree]*kaijo[right-1]);
        int lfree = h-1 - down;
        mint l = kaijo[lfree+down-1]/(kaijo[lfree]*kaijo[down-1]);
        ans += (r*l)*mint(2).pow(free);

        if(dummy%2 == 0){
            right++;
        }else{
            down++;
        }
        dummy++;
    }
    cout << ans.val() << endl;

    return 0;
}