#include <bits/stdc++.h>

#include <atcoder/modint>
using namespace std;
using mint = atcoder::modint998244353;
void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fast_io();
    int n;
    cin >> n;
    vector<vector<mint>> dp(n + 1, vector<mint>(3, 0));
    vector<mint> p26(n, 1);
    for (int i = 1; i < n; i++) {
        p26[i] = p26[i - 1] * 26;
    }
    dp[0][0] = 1;
    mint ans = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < 3; j++) {
            dp[i + 1][j] += dp[i][j] * 25;
            dp[i + 1][(j + 1) % 3] += dp[i][j];
            if (j == 2) {
                ans += dp[i][j] * p26[n - i - 1];
            }
        }
    }
    cout << ans.val() << endl;
}