N=int(input())
S=input()
mod=998244353
DP=[[[0]*2 for _ in range(2)] for _ in range(N+1)]

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

    DP[i+1][1][1]+=DP[i][0][1]
    
    now=ord(S[i])-ord("a")

    if now!=0:
        DP[i+1][1][1]+=DP[i][0][0]
        DP[i+1][1][1]+=(now-1)*DP[i][1][0]
        DP[i+1][0][1]+=(now-1)*DP[i][0][0]
        DP[i+1][0][0]+=DP[i][0][0]
        DP[i+1][1][0]+=DP[i][1][0]
    else:
        DP[i+1][1][0]+=DP[i][0][0]
    
    for j in range(2):
        for k in range(2):
            DP[i+1][j][k]%=mod

print(DP[N][1][1])