#include<bits/stdc++.h>

using namespace std;
#define ll long long
#define pii pair<int, int>
#define ld long double
#define all(a) (a).begin(), (a).end()

#define int int64_t

const int MOD = 998244353;
const int G1 = 31;
const int G2 = 128805723;

int pw(int x, int n) {
    int res = 1;
    while (n) {
        if (n % 2 == 0) {
            x = (x * x) % MOD;
            n /= 2;
        } else {
            res = (res * x) % MOD;
            n--;
        }
    }
    return res;
}

void fft(vector<int>& a, bool inv = false) {
    int k = 0;
    while ((1 << k) < (int)a.size()) ++k;
    int n = a.size();
    for (int i = 0; i < n; ++i) {
        int j = 0;
        for (int l = 0; l < k; ++l) {
            if (i & (1 << l)) {
                j |= (1 << (k - l - 1));
            }
        }
        if (i < j) {
            swap(a[i], a[j]);
        }
    }
    for (int l = 1; l < n; l *= 2) {
        int w_n = pw(inv ? G2 : G1, (MOD - 1) / 2 / l);
        for (int i = 0; i < n; i += 2 * l) {
            int w = 1;
            for (int j = 0; j < l; ++j) {
                int x = a[i + j], y = (a[i + j + l] * w) % MOD;
                a[i + j] = (x + y) % MOD;
                a[i + j + l] = (x - y + MOD) % MOD;
                w = (w * w_n) % MOD;
            }
        }
    }
    if (inv) {
        int div = pw(n, MOD - 2);
        for (int i = 0; i < n; ++i) {
            a[i] = (a[i] * div) % MOD;
        }
    }
}

const int MAXN = (1 << 20);
int fact[MAXN], invf[MAXN];

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    fact[0] = 1;
    for (int i = 1; i < MAXN; ++i) {
        fact[i] = (fact[i - 1] * i) % MOD;
    }
    invf[MAXN - 1] = pw(fact[MAXN - 1], MOD - 2);
    for (int i = MAXN - 1; i > 0; --i) {
        invf[i - 1] = (invf[i] * i) % MOD;
    }

    int n, m;
    cin >> n >> m;
    vector<int> arr(m + 1);
    for (int i = 0; i <= m; ++i) {
        arr[i] = (invf[m - i] * invf[m - i]) % MOD;
        arr[i] = (arr[i] * invf[i]) % MOD;
    }
    arr.resize(MAXN);
    fft(arr);
    for (int& x : arr) {
        x = pw(x, n);
    }
    fft(arr, true);
    int ans = 0;
    int sgn = 1;
    for (int sum = 0; sum <= n * m; ++sum, sgn *= -1) {
        ans += sgn * fact[n * m - sum] * arr[sum];
        ans %= MOD;
    }
    ans = (ans % MOD + MOD) % MOD;
    ans = (ans * pw(fact[m], 2 * n)) % MOD;
    cout << ans << endl;


    return 0;
}