#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

std::vector<std::vector<long long>> mul(const std::vector<std::vector<long long>> &v1, const std::vector<std::vector<long long>> &v2, long long mod = 1001001001001001001)
{
    std::vector<std::vector<long long>> ans;
    if (v1[0].size() != v2.size())
    {
        std::cout << "matrix mul size error: (" << v1[0].size() << ", " << v2.size() << ")" << std::endl;
        std::exit(1);
    }
    ans.resize(v1.size(), std::vector<long long> (v2[0].size()));
    for (int i = 0; i < v1.size(); ++i) for (int j = 0; j < v2[0].size(); ++j) for (int k = 0; k < v1[0].size(); ++k) ans[i][j] = (ans[i][j] + v1[i][k] * v2[k][j]) % mod;
    return ans;
}

std::vector<std::vector<long long>> pow(std::vector<std::vector<long long>> v, long long k, long long mod = 1001001001001001001)
{
    std::vector<std::vector<long long>> ans;
    if (v.size() != v[0].size())
    {
        std::cout << "matrix pow size error: (" << v.size() << ", " << v[0].size() << ")" << std::endl;
        std::exit(1);
    }
    ans.resize(v.size(), std::vector<long long> (v.size()));
    for (int i = 0; i < v.size(); ++i) ans[i][i] = 1;
    for (; k > 0; k >>= 1, v = mul(v, v, mod)) if (k & 1) ans = mul(v, ans, mod);
    return ans;
}

int main()
{
  const int mod = 998244353;
  long long n, m;
  cin >> n >> m;
  vector<vector<long long>> mat(2, vector<long long> (2));
  mat[0][1] = 1;
  mat[1][0] = m % mod;
  mat[1][1] = (m - 1) % mod;
  auto res = pow(mat, n, mod);
  long long ans = res[0][0];
  cout << ans << endl;
}