from typing import List, Tuple, Callable, TypeVar, Optional
import sys
import itertools
import heapq
import bisect
import math
from collections import deque, defaultdict
from functools import lru_cache, cmp_to_key

input = sys.stdin.readline

if __file__ != 'prog.py':
    sys.setrecursionlimit(10 ** 6)


def readints(): return map(int, input().split())
def readlist(): return list(readints())
def readstr(): return input()[:-1]
def readlist1(): return list(map(lambda x: int(x) - 1, input().split()))


N = int(input())
A = [ord(c) - ord('a') for c in readstr()]
mod = 998244353

dp = [[0, 0], [0, 0]]
dp[0][0] = 1
for i in range(N):
    ndp = [[0, 0], [0, 0]]
    ndp[1][1] += dp[1][1] * 25
    ndp[1][1] += dp[0][1]
    ndp[0][1] += dp[0][1] * 25

    if A[i] == 0:
        ndp[1][0] += dp[0][0]
    else:
        ndp[1][1] += dp[1][0] * (A[i] - 1)
        ndp[1][0] += dp[1][0]
        ndp[1][1] += dp[0][0]
        ndp[0][1] += dp[0][0] * (A[i] - 1)
        ndp[0][0] += dp[0][0]
    for j in range(2):
        for k in range(2):
            ndp[j][k] %= mod
    dp = ndp
print(dp[1][1])