#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
using mint = modint998244353;
const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<vector<mint>> dp(n + 1, vector<mint>(3));
	dp[0][0] = 1;
	mint ans = 0;
	rep(i, n) {
		dp[i + 1][0] += dp[i][0] * 25 + dp[i][2];
		dp[i + 1][1] += dp[i][1] * 25 + dp[i][0];
		dp[i + 1][2] += dp[i][2] * 25 + dp[i][1];
		ans += dp[i][2] * pow_mod(26, n - i - 1, mod);
	}
	cout << ans.val() << endl;
	return 0;
}