#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define rep(i,n) for(int i=0;i<n;i++)
#define rrep(i,n) for(int i=n-1;i>=0;i--)
#define rrep2(i,n,k) for(int i=n-1;i>=n-k;i--)
#define vll(n,i) vector<long long>(n,i)
#define v2ll(n,m,i) vector<vector<long long>>(n,vll(m,i))
#define v3ll(n,m,k,i) vector<vector<vector<long long>>>(n,v2ll(m,k,i))
#define v4ll(n,m,k,l,i) vector<vector<vector<vector<long long>>>>(n,v3ll(m,k,l,i))
#define all(v) v.begin(),v.end()
#define chmin(k,m) k = min(k,m)
#define chmax(k,m) k = max(k,m)
#define Pr pair<ll,ll>
#define Tp tuple<int,int,int>
#define riano_ std::ios::sync_with_stdio(false);std::cin.tie(nullptr)
using Graph = vector<vector<int>>;

const ll mod = 998244353;
template<uint64_t mod>
struct modint{
    uint64_t val;
    constexpr modint(const int64_t val_=0) noexcept:val((val_%int64_t(mod)+int64_t(mod))%int64_t(mod)){}
    constexpr modint operator-() const noexcept{
        return modint(*this)=mod-val;
    }
    constexpr modint operator+(const modint rhs) const noexcept{
        return modint(*this)+=rhs;
    }
    constexpr modint operator-(const modint rhs) const noexcept{
        return modint(*this)-=rhs;
    }
    constexpr modint operator*(const modint rhs) const noexcept{
        return modint(*this)*=rhs;
    }
    constexpr modint operator/(const modint rhs) const noexcept{
        return modint(*this)/=rhs;
    }
    constexpr modint &operator+=(const modint rhs) noexcept{
        val+=rhs.val;
        val-=((val>=mod)?mod:0);
        return (*this);
    }
    constexpr modint &operator-=(const modint rhs) noexcept{
        val+=((val<rhs.val)?mod:0);
        val-=rhs.val;
        return (*this);
    }
    constexpr modint &operator*=(const modint rhs) noexcept{
        val=val*rhs.val%mod;
        return (*this);
    }
    constexpr modint &operator/=(modint rhs) noexcept{
        uint64_t ex=mod-2;
        modint now=1;
        while(ex){
            now*=((ex&1)?rhs:1);
            rhs*=rhs,ex>>=1;
        }
        return (*this)*=now;
    }
    modint & operator++(){
        val++;
        if (val == mod) val = 0;
        return *this;
    }
    modint operator++(int){
        modint<mod> res = *this;
        ++*this;
        return res;
    }
    constexpr bool operator==(const modint rhs) noexcept{
        return val==rhs.val;
    }
    constexpr bool operator!=(const modint rhs) noexcept{
        return val!=rhs.val;
    }
    friend constexpr ostream &operator<<(ostream& os,const modint x) noexcept{
        return os<<(x.val);
    }
    friend constexpr istream &operator>>(istream& is,modint& x) noexcept{
        uint64_t t;
        is>>t,x=t;
        return is;
    }
};
typedef modint<mod> mint;
#define vm(n,i) vector<mint>(n,i)
#define v2m(n,m,i) vector<vector<mint>>(n,vm(m,i))
#define v3m(n,m,k,i) vector<vector<vector<mint>>>(n,v2m(m,k,i))
#define v4m(n,m,k,l,i) vector<vector<vector<vector<mint>>>>(n,v3m(m,k,l,i))


//累乗 aのb乗、正しmを法として求める
long long pw(long long a,long long b,long long m){
    if(b==0) return 1;
    else if(b%2==0){
        long long x = pw(a,b/2,m);
        return (x*x)%m;
    }
    else{
        long long x = pw(a,b-1,m);
        return (a*x)%m;
    }
}


mint sum_r(mint a,mint r, mint n){
    if(n==0) return mint(0);
    mint res = a*mint(pw(r.val,n.val,mod)-1)/(r-mint(1));
    return res;
}


//Combination2
//10^6くらいまで
//modはグローバルに定義しておく
long long modinv(long long a, long long m) {
    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m;
    if (u < 0) u += m;
    return u;
}
vector<ll> fact;
vector<ll> invf;
ll comb(ll n,ll k){
    if(n<0||k<0||k>n) return 0LL;
    else{
        ll a = fact[n]*invf[k]%mod;
        a = a*invf[n-k]%mod;
        return a;
    }
}
    
int main() {
    riano_; mint ans = 0;
    ll N,M; cin >> N >> M;
    //main関数内に以下ペースト
    //N:max
    ll L = max(N+1,M+1);
    fact.assign(L+1,1LL);
    invf.assign(L+1,1LL);
    rep(i,L) fact[i+1] = fact[i]*(i+1)%mod;
    rep(i,L+1) invf[i] = modinv(fact[i],mod);

    ans = mint(M)*(mint(pw(M,2*N,mod))-mint(pw(M-1,2*N,mod)));
    for(ll i=2;i<=M;i++){
        if(i-1>N) break;
        mint f = mint(pw(M-i,2*(N-i+1),mod))*mint(comb(N,i-1))*mint(pw(i,i-2,mod))*mint(pw(2,i-1,mod))*mint(fact[i-1]);
        ans -= f*mint(comb(M,i));
    }
    
    cout << ans << endl;
}