import java.util.*;

@SuppressWarnings("unused")
public class Main {

  private static void solve() {
    int n = ni();

    long[] g = new long[n / 3 + 2];

    int mod = 998244353;
    int[][] fif = enumFIF(3000, mod);

    g[0] = pow(26, n, mod);

    for (int k = 1; k < g.length; k ++) {
      for (int i = k * 3; i <= n; i ++) {
        long cur = pow(26, n - i, mod);

        cur *= CX(i - 1, k * 3 - 1, mod, fif);
        cur %= mod;
        cur *= pow(25, i - k * 3, mod);
        cur %= mod;

        g[k] += cur;
        g[k] %= mod;
      }
    }

    long ret = 0;
    for (int i = 0; i < g.length - 1; i ++) {
      ret += (g[i] - g[i + 1] + mod) % mod * i % mod;
      ret %= mod;
    }
    System.out.println(ret);
  }


  public static int[][] enumFIF(int n, int mod) {
      int[] f = new int[n + 1];
      int[] invf = new int[n + 1];
      f[0] = 1;
      for (int i = 1; i <= n; i++) {
          f[i] = (int) ((long) f[i - 1] * i % mod);
      }
      long a = f[n];
      long b = mod;
      long p = 1, q = 0;
      while (b > 0) {
          long c = a / b;
          long d;
          d = a;
          a = b;
          b = d % b;
          d = p;
          p = q;
          q = d - c * q;
      }
      invf[n] = (int) (p < 0 ? p + mod : p);
      for (int i = n - 1; i >= 0; i--) {
          invf[i] = (int) ((long) invf[i + 1] * (i + 1) % mod);
      }
      return new int[][] { f, invf };
  }
  public static long CX(long n, long r, int p, int[][] fif) {
      if (n < 0 || r < 0 || r > n)
          return 0;
      int np = (int) (n % p), rp = (int) (r % p);
      if (np < rp)
          return 0;
      if (n == 0 && r == 0)
          return 1;
      int nrp = np - rp;
      if (nrp < 0)
          nrp += p;
      return (long) fif[0][np] * fif[1][rp] % p * fif[1][nrp] % p * CX(n / p, r / p, p, fif) % p;
  }

  public static long pow(long x, long n, long m) {
      assert (n >= 0 && m >= 1);
      long ans = 1;
      while (n > 0) {
          if (n % 2 == 1)
              ans = (ans * x) % m;
          x = (x * x) % m;
          n /= 2;
      }
      return ans;
  }

  public static void main(String[] args) {
    new Thread(null, new Runnable() {
      @Override
      public void run() {
        long start = System.currentTimeMillis();
        String debug = args.length > 0 ? args[0] : null;
        if (debug != null) {
          try {
            is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug));
          } catch (Exception e) {
            throw new RuntimeException(e);
          }
        }
        reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768);
        solve();
        out.flush();
        tr((System.currentTimeMillis() - start) + "ms");
      }
    }, "", 64000000).start();
  }

  private static java.io.InputStream is = System.in;
  private static java.io.PrintWriter out = new java.io.PrintWriter(System.out);
  private static java.util.StringTokenizer tokenizer = null;
  private static java.io.BufferedReader reader;

  public static String next() {
    while (tokenizer == null || !tokenizer.hasMoreTokens()) {
      try {
        tokenizer = new java.util.StringTokenizer(reader.readLine());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
    return tokenizer.nextToken();
  }

  private static double nd() {
    return Double.parseDouble(next());
  }

  private static long nl() {
    return Long.parseLong(next());
  }

  private static int[] na(int n) {
    int[] a = new int[n];
    for (int i = 0; i < n; i++)
      a[i] = ni();
    return a;
  }

  private static char[] ns() {
    return next().toCharArray();
  }

  private static long[] nal(int n) {
    long[] a = new long[n];
    for (int i = 0; i < n; i++)
      a[i] = nl();
    return a;
  }

  private static int[][] ntable(int n, int m) {
    int[][] table = new int[n][m];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[i][j] = ni();
      }
    }
    return table;
  }

  private static int[][] nlist(int n, int m) {
    int[][] table = new int[m][n];
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        table[j][i] = ni();
      }
    }
    return table;
  }

  private static int ni() {
    return Integer.parseInt(next());
  }

  private static void tr(Object... o) {
    if (is != System.in)
      System.out.println(java.util.Arrays.deepToString(o));
  }
}