#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint = atcoder::static_modint<998244353>;
// using mint = atcoder::static_modint<1000000007>;
using ld = long double;
using ll = long long;
#define mp(a,b) make_pair(a,b)
#define rep(i,s,n) for(int i=s; i<(int)n; i++)
using vl = vector<ll>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vvvvl = vector<vvvl>;
const vector<int> dx{1,0,-1,0},dy{0,1,0,-1};

template<class T>
struct Factorial{
    Factorial(int _n):fac(_n+1,1),invfac(_n+1,1){
        for(int i=1; i<=_n; i++){
            fac[i]=fac[i-1]*i;
            invfac[i]/=fac[i];
        }
    };
    T nCr(int n,int r){
        if(0<=r && r<=n)return fac[n]*invfac[r]*invfac[n-r];
        else return 0;
    }
    T nPr(int n,int r){
        if(0<=r && r<=n)return fac[n]*invfac[n-r];
        else return 0;
    }
    T sum(int a,int b){
        // \Sigma_{i\in[0,a],j\in[0,b]}(i+j)Ciを計算
        return nCr(a+b+2,a+1)-1;
    }
    vector<T> fac,invfac;
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    const int m=500000;
    ll h,w;cin >> h >> w;
    Factorial<mint> F(m);
    if(min(h,w)==1){
        cout << 1;
        return 0;
    }

    mint ans=0;
    rep(i,1,h+w+3){
        if(h*w-(h+w-1)-(i-1)>=0)ans+=mint(2).pow(h*w-(h+w-1)-(i-1))*F.nCr(h-2,(i-1)/2)*F.nCr(w-1,i/2);
        // cout << (F.nCr(h-2,i/2)*F.nCr(w-1,(i+1)/2)).val() << " " << i << "\n";
    }
    cout << ans.val();
}