N=int(input())
S=list(input())
mod=998244353
for i in range(N):
  S[i]=ord(S[i])-ord('a')
DP=[[0]*4 for i in range(N+1)]
DP[0][0]=1
for i in range(N):
  DP[i+1][3]+=DP[i][3]*25
  DP[i+1][2]+=DP[i][2]*25
  DP[i+1][3]+=DP[i][2]
  if S[i]==0:
    DP[i+1][1]+=DP[i][0]
  else:
    DP[i+1][0]+=DP[i][0]
    DP[i+1][3]+=DP[i][0]
    DP[i+1][2]+=DP[i][0]*(S[i]-1)
    DP[i+1][1]+=DP[i][1]
    DP[i+1][3]+=DP[i][1]*(S[i]-1)
  for j in range(4):
    DP[i+1][j]%=mod
print(DP[N][3])