#include "bits/stdc++.h"
using namespace std;
#define all(x) begin(x),end(x)
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#define debug(a) cerr << "(" << #a << ": " << a << ")\n";
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int mxN = 1<<20, oo = 1e9;
const long long MOD =  998244353;
class mint {
public:
    int d;
    mint () {d=0;}
    mint (long long _d) : d(_d%MOD){};
    mint operator*(const mint& o) const {
        return ((ll)d*o.d)%MOD;
    }
    mint operator+(const mint& o) const {
        long long tmp = d+o.d;
        if(tmp>=MOD) tmp-=MOD;
        return tmp;
    }
    mint operator-(const mint& o) const {
        long long tmp = d-o.d;
        if(tmp<0) tmp+=MOD;
        return tmp;
    }
    mint operator^(long long b) const {
        mint tmp = 1;
        mint power = *this;
        while(b) {
            if(b&1) {
                tmp = tmp*power;
            }
            power = power*power;
            b/=2;
        }
        return tmp;
    }
    mint operator/(const mint& o) {
        return *this * (o^(MOD-2));
    }
    bool operator==(const mint& o) {
        return d==o.d;
    }
    friend mint& operator+=(mint& a, const mint& o) {
        a.d+=o.d;
        if(a.d>=MOD) a.d-=MOD;
        return a;
    }
};
typedef mint cd;
void revperm(cd* in, int n) {
    for(int i=0,j=0;i<n;++i) {
        if(i<j) swap(in[i],in[j]);
		for(int k = n >> 1; (j ^= k) < k; k >>= 1);
    }
}
cd w[mxN+1]; // stores w^j for each j in [0,n-1]
void precomp() {
    w[0] = 1;
    int pw = (MOD-1)/mxN;
    w[1] = mint(3)^pw;
    for(int i= 2;i<=mxN;++i) {
        w[i] = w[i-1]*w[1];
    }
}
void fft(cd* in, int n, bool reverse=false) {
    int lg = __lg(n);
    assert(1<<lg == n);
    int stride = mxN/n;
    revperm(in,n);
    for(int s=1;s<=lg;++s) {
        int pw = 1<<s;
        int mstride = stride*(n>>s);
        for(int j=0;j<n;j+=pw) {
            // do FFT merging on out array
            cd* even = in+j, *odd = in+j+pw/2;
            for(int i=0;i<pw/2;++i) {
                cd& power = w[reverse?mxN-mstride*i:mstride*i];
                auto tmp = power*odd[i];
                odd[i] = even[i] - tmp;
                even[i] = even[i] + tmp;
            }
        }
    }
    if(reverse) {
        mint fac = mint(1)/n;
        for(int i=0;i<n;++i) in[i]=in[i]*fac;
    }
}
int total;

vector<cd> polypow(vector<cd>& a, int len, int k) {
    int ptwo=1;
    while(ptwo<len) ptwo*=2;
    a.resize(ptwo);
    fft(a.data(),ptwo); 
    for(int i=0;i<ptwo;++i) 
        a[i] = a[i]^k;
    fft(a.data(),ptwo,true);
    return a;
}
const int mxF = 2e6+2;
mint fact[mxF], ifact[mxF];
mint ncr(int a, int b) {
    if(b>a or a<0 or b<0) return 0;
    return fact[a]*ifact[b]*ifact[a-b];
}
void precomp2() {
    fact[0]=1;
    for(int i=1;i<mxF;++i) {
        fact[i]=fact[i-1]*i;
    }
    ifact[mxF-1] = mint(1)/fact[mxF-1];
    for(int i=mxF-2;i>=0;--i) {
        ifact[i]=ifact[i+1]*(i+1);
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    precomp();
    precomp2();
    int n,m; cin >> n >> m;
    vector<cd> a(m+1);
    a[0]=1;
    for(int i=1;i<=m;++i) {
        a[i] = a[i-1]*(m-i+1);
    }
    for(int i=1;i<=m;++i) {
        a[i] =a[i]* ncr(m,i);
    }
    a = polypow(a,n*m+1,n);
    mint ans=0;
    mint sgn=1;
    for(int k=0;k<=n*m;++k) {
        ans+=fact[n*m-k]*sgn*a[k];

        sgn=mint(0)-sgn;
    }
    cout << ans.d << '\n';

}