#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second

const ll MOD = 998244353;
const ll INF = 1LL << 60;
const ll MAX_N = 2e5;

ll dp[3001][1001][3];

int main(){
    ll n;
    cin >> n;

    dp[0][0][0] = 1;
    for(ll i=1; i<=n; i++){
        for(ll j=0; j<=1000; j++){
            //cの場合
            dp[i][j][1] = (dp[i][j][1] + dp[i-1][j][0])%MOD;

            //oの場合
            dp[i][j][2] = (dp[i][j][2] + dp[i-1][j][1])%MOD;

            //nの場合
            if(j <= 999) dp[i][j+1][0] = (dp[i][j+1][0] + dp[i-1][j][2])%MOD;

            //その他
            dp[i][j][0] = (dp[i][j][0] + dp[i-1][j][0]*25)%MOD;
            dp[i][j][1] = (dp[i][j][1] + dp[i-1][j][1]*25)%MOD;
            dp[i][j][2] = (dp[i][j][2] + dp[i-1][j][2]*25)%MOD;
        }
    }

    ll ans = 0;
    for(ll j=0; j<=1000; j++) for(ll k=0; k<=2; k++){
        ans = (ans + dp[n][j][k]*j)%MOD;
    }

    cout << ans << endl;
}