#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using pi = pair<int,int>;
using pl = pair<ll,ll>;
#define all(x) x.begin(),x.end()
#define rep(i,j,n) for (long long i = j; i < (long long)(n); i++)
const long long MOD = 1000000007;
const long long MOD2 = 998244353;
const int INF = ((1<<30)-1);
const long long LINF = (1LL<<60);
const double PI = 3.141592653589793238;
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {a = b;return 1;} return 0;
}
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {a = b;return 1;} return 0;
}
//--------------------------------------------------

template<int MOD> struct Fp {  
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) val += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator > (const Fp& r) const noexcept {
		return this->val > r.val;
	}
	constexpr bool operator < (const Fp& r) const noexcept {
		return this->val < r.val;
	}
	constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};
using mint = Fp<MOD2>;

const int M = 202020;
mint fac[202020];
mint inv[202020];

mint C(int n, int k){
    return fac[n] * inv[k] * inv[n-k];
}

mint P(int n , int k){
    return fac[n] * inv[n-k];
}

int solve(){
    int n,m; cin >> n >> m;
    fac[0] = 1;
    rep(i,1,M)fac[i] = fac[i-1] * i;
    inv[M-1] = modpow(fac[M-1],MOD2-2);
    for(int i = M-2; i >= 0; --i)inv[i] = inv[i+1] * (i+1);
    mint ans = modpow(mint(m) , 2*n+1);
    for(int i = 1; i <= min(n+1 , m); i++){
        mint s = C(m , i);
        if(i > 1)s *= modpow(mint(i) , i-2);
        s *= modpow(mint(2) , i-1);
        s *= P(n , i-1);
        s *= modpow(mint(m-i) , 2*(n-i+1));
        ans -= s;
    }
    cout << ans << endl;


    return 0;
}

int main(){
    cout << fixed << setprecision(20);
    ios::sync_with_stdio(0), cin.tie(0);
    int t = 1; 
    //cin >> t;
    for(int i = 0; i < t; i++){
        solve();
    }
	return 0;
}