#include <bits/stdc++.h>
using namespace std;
#define int    long long
#define fs     first
#define sc     second
#define all(x) (x).begin(), (x).end()

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vpii;

const ll mod = 998244353;
const ll MAXN = 1'000'003;

int qpow(int a, int e, int mo) {
	int ans = 1;
	for (; e; a = a * a % mo) {
		if (e & 1) {
			ans = ans * a % mo;
		}
		e /= 2;
	}
	return ans;
}

namespace ntt{
const int root=5;
int base=1;
vector<int> roots;

void ensure_base(int nbase){
	if(nbase<=base)return;
	roots.resize(nbase);
	for(int mh=base;mh<<1 <= nbase;mh<<=1){
		int wm=qpow(root,(mod-1)/(mh<<1),mod);
		roots[mh]=1;
		for(int i=1;i<mh;i++)
			roots[i+mh]=(ll)roots[i+mh-1]*wm%mod;
	}
	base=nbase;
}

void fft(int a[],int n,int sign){
	ensure_base(n);
	for(int i=1,j=0; i<n-1;i++){
		for(int k=n>>1;(j^=k)<k;k>>=1);
		if(i<j)swap(a[i],a[j]);
	}
	for(int m,mh=1;(m=mh<<1)<=n;mh=m)
		for(int i=0;i<n;i+=m)
			for(int j=i;j<i+mh;j++){
				int y=(ll)a[j+mh]*roots[j-i+mh]%mod;
				if((a[j+mh]=a[j]-y)<0)a[j+mh]+=mod;
				if((a[j]+=y)>=mod)a[j]-=mod;
			}
		if(sign<0){
			int inv=qpow(n,mod-2,mod);
			for(int i=0;i<n;i++)a[i]=a[i]*inv%mod;
			reverse(a+1,a+n);
		}
}


vector<int> convolve(vector<int> x, vector<int> y) {
	int n = x.size() + y.size() - 1, sz = 1;
	while(sz<n)sz<<=1;
	x.resize(sz);
	y.resize(sz);
	fft(x.data(),sz,+1);
	fft(y.data(),sz,+1);
	for(int i=0;i<sz;i++)
		x[i]=ll(x[i])*y[i]%mod;
	fft(x.data(),sz,-1);
	x.resize(n);
	return x;
}
}




vi Pow(vi A, int e) {
	vi ans = {1};
	for (; e; A = ntt::convolve(A, A)) {
		if (e & 1) {
			ans = ntt::convolve(ans, A);
		}
		e /= 2;
	}
	return ans;
}

int Fac[MAXN];
int IFac[MAXN];

int C(int a, int b) {
	if (b > a || b < 0)
		return 0;
	return Fac[a] * IFac[a - b] % mod * IFac[b] % mod;
}

int n, m;

void problem() {
	cin >> n >> m;
	vi A(m + 1);
	for (int i = 0; i <= m; i++) {
		A[i] = C(m, i) * IFac[m - i] % mod;
    }
	vi F = Pow(A, n);
	int ans = 0;
	for (int i = 0; i <= n * m; i++) {
		F[i] = F[i] * Fac[n * m - i] % mod;
		ans = (ans + (1 - 2 * (i & 1)) * F[i] + mod) % mod;
	}

	cout << ans * qpow(Fac[m], n, mod) % mod << "\n";
}

int32_t main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	Fac[0] = 1;
	for (int i = 1; i < MAXN; i++)
		Fac[i] = Fac[i - 1] * i % mod;
	IFac[MAXN - 1] = qpow(Fac[MAXN - 1], mod - 2, mod);
	for (int i = MAXN - 1; i > 0; i--)
		IFac[i - 1] = IFac[i] * i % mod;
	problem();

	return 0;
}