#include <stdio.h>

int main () {
  int n = 0;
  
  int res = 0;
  
  long long ans = 0LL;
  long long mod_num = 998244353LL;
  
  long long dp[3001][3] = {};
  long long pow26[3000] = {};
  
  res = scanf("%d", &n);
  
  pow26[0] = 1LL;
  for (int i = 1; i < n; i++) {
    pow26[i] = (pow26[i-1]*26LL)%mod_num;
  }
  
  dp[0][0] = 1LL;
  for (int i = 0; i < n; i++) {
    dp[i+1][0] = (dp[i][0]*25LL)%mod_num;
    dp[i+1][1] = (dp[i][1]*25LL)%mod_num;
    dp[i+1][2] = (dp[i][2]*25LL)%mod_num;
    dp[i+1][0] = (dp[i+1][0]+dp[i][2])%mod_num;
    dp[i+1][1] = (dp[i+1][1]+dp[i][0])%mod_num;
    dp[i+1][2] = (dp[i+1][2]+dp[i][1])%mod_num;
    ans += (dp[i][2]*pow26[n-i-1])%mod_num;
  }
  
  printf("%lld\n", ans%mod_num);
  return 0;
}