#include <iostream>
#include <vector>
#include <cstdio>
#include <algorithm>
#include <cmath>
#include <cstdlib>
#include <string>
#include <cstring>
#include <queue>
#include <stack>
#include <functional>
#include <map>
#include <set>
#include <bitset>
#include <ctime>
#include <cassert>
#include <complex>

const int INF = 0x3f3f3f3f;
const long long INFLL = 0x3f3f3f3f3f3f3f3fll;
#define memset0(x) memset(x, 0, sizeof(x))
#define memsetM1(x) memset(x, -1, sizeof(x))
#define memsetINF(x) memset(x, INF, sizeof(x))

using namespace std;
using ll = long long;
const ll MOD = 998244353;

const int P = 998244353, N = 1e6 + 5, g = 3;

long long power(ll a, int b)
{
	long long ans = 1;
	long long t;
	for (t = a; b; b >>= 1)
	{
		if (b & 1)	ans *= t; ans %= P;
		t *= t; t %= P;
	}
	return ans;
}

ll wn[N + 5];
void get_wn()
{
	for (int i = 0; i < 23; i++)
	{
		int t = 1 << i;
		wn[i] = power(g, (P - 1) / t);
	}
}

void change(ll y[], int n)
{
	for (int i = 1, j = n >> 1; i < n - 1; i++)
	{
		if (i < j)	swap(y[i], y[j]);
		int k = n / 2;
		while (j >= k && j)
		{
			j -= k;
			k >>= 1;
		}
		if (j < k)	j += k;
	}
}

//sgn == -1 : Inverse
void ntt(ll y[], int n, int sgn = 1)
{
	change(y, n);
	int id = 0;
	for (int h = 2; h <= n; h <<= 1)
	{
		id++;
		for (int j = 0; j < n; j += h)
		{
			ll w = 1;
			for (int k = j; k < j + h / 2; k++)
			{
				ll u = y[k];
				ll t = 1ll * w * y[k + h / 2] % P;
				y[k] = (u + t) % P;
				y[k + h / 2] = ((u - t) % P + P) % P;
				w = (1ll * w * wn[id]) % P;
			}
		}
	}

	if (sgn == -1)
	{
		for (int i = 1; i < n / 2; i++)
			swap(y[i], y[n - i]);
		ll inv = power(n, P - 2);
		for (int i = 0; i < n; i++)
			y[i] = 1ll * y[i] * inv % P;
	}
}

int sum[N + 10];
char str1[N + 10], str2[N + 10];
ll x2[2 * N + 10];
ll fac[N], inv[N], invFac[N];
int n, m;

ll getC(int a, int b)
{
	if (a - b < 0)
	{
		return 0;
	}
	return fac[a] * invFac[b] % MOD * invFac[a - b] % MOD;
}

ll getA(int a, int b)
{
	if (a - b < 0)
	{
		return 0;
	}
	return fac[a] * invFac[a - b] % MOD;
}

int main()
{
	
	cin >> n >> m;
	fac[0] = fac[1] = inv[0] = inv[1] = invFac[0] = invFac[1] = 1;
	for (int i = 2; i <= n * m; i++)
	{
		fac[i] = fac[i - 1] * i % MOD;
		inv[i] = ll(MOD - MOD / i) * inv[MOD % i] % MOD;
		invFac[i] = invFac[i - 1] * inv[i] % MOD;
	}
	get_wn();
	int d = 1;
	while (d <= n * m)
	{
		d <<= 1;
	}
	for (int i = 0; i <= m; i++)
	{
		x2[i] = getC(m, i) * getA(m, i) % MOD;
	}


	ntt(x2, d);
	for (int i = 0; i < d; i++)
		x2[i] = power(x2[i], n);
	ntt(x2, d, -1);
	
	ll ans = 0;
	ll psgn = 1;
	for (int i = 1; i <= n * m; i++)
	{
		ans = (ans + psgn * x2[i] * fac[n * m - i] % MOD) % MOD;
		psgn *= -1;
	}
	ans = ((fac[n * m] - ans) % MOD + MOD) % MOD;
	cout << ans << endl;

	return 0;
}