import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
import pypyjit
pypyjit.set_param('max_unroll_recursion=-1')
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd
mod = 998244353

n = int(input())

#nCk
def com(n,mod):
  fact = [1,1]
  factinv = [1,1]
  inv = [0,1]
  for i in range(2,n+1):
    fact.append((fact[-1]*i)%mod)
    inv.append((-inv[mod%i]*(mod//i))%mod)
    factinv.append((factinv[-1]*inv[-1])%mod)
  return fact, factinv

f,fi = com(5000, mod)
def ncr(n,r):
  return f[n] * fi[r] * fi[n-r] % mod
ans = 0

for k in range(1,n):
  if 3 * k > n: break
  for i in range(3*k-1,n):
    tmp = ncr(i,3*k-1) * pow(25, i-3*k+1,mod) * pow(26, n-i-1,mod)
    ans += tmp
    ans %= mod

print(ans)