import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
import time
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines
write=sys.stdout.write

N=int(readline())
S=[ord(s)-97 for s in readline().rstrip()]
mod=998244353
dp0,dp1=0,0
cnt=0
for s in S:
    dp0,dp1=(dp0*25)%mod,(dp0+dp1*25)%mod
    if s:
        if cnt==0:
            dp1+=1
            dp0+=s-1
        elif cnt==1:
            dp1+=s-1
    if s==0:
        cnt+=1
ans=dp1%mod
print(ans)