#include <bits/stdc++.h>
#include <atcoder/modint>
#include <atcoder/convolution>
using namespace std;

using Mint = atcoder::modint998244353;

int main()
{
    int N, M;
    cin >> N >> M;
    if (M == 1)
    {
        cout << 1 << endl;
        return 0;
    }
    vector<vector<Mint>> ok(N + 1, vector<Mint>(M + 1));
    vector<Mint> psum(N + 1);
    for (int j = 2; j <= M; ++j)
        ok[1][j] = 1;
    psum[0] = 1;
    psum[1] = M - 1;
    for (int i = 2; i <= N; ++i)
    {
        for (int j = 2; j <= M; ++j)
        {
            ok[i][j] = psum[i - 1];
            if (i >= j)
                ok[i][j] -= psum[i - j] - ok[i - j][j];
            psum[i] += ok[i][j];
        }
    }
    cout << (Mint(M).pow(N) - psum[N]).val() << endl;
}