N = int(input())
S = input()
A = [ord(s) - ord('a') for s in S]
P = 998244353

dp = [[[0] * 2 for _ in range(2)] for _ in range(N)]

if A[0] > 0:
    dp[0][0][0] = A[0] - 1
    dp[0][0][1] = 1
    dp[0][1][0] = 1
    dp[0][1][1] = 0
else:
    dp[0][0][0] = 0
    dp[0][0][1] = 0
    dp[0][1][0] = 0
    dp[0][1][1] = 1
for i in range(N-1):
    dp[i+1][1][0] =(dp[i+1][1][0] + dp[i][0][0]) % P
    dp[i+1][0][0] =(dp[i+1][0][0] + dp[i][0][0] * 25) % P

    if A[i+1] == 0:
        dp[i+1][1][1] =(dp[i+1][1][1] +  dp[i][0][1]) % P
    else:
        dp[i+1][0][1] =(dp[i+1][0][1] + dp[i][0][1]) % P
        dp[i+1][0][0] =(dp[i+1][0][0] + dp[i][0][1] * (A[i+1] - 1)) % P
        dp[i+1][1][0] =(dp[i+1][1][0] + dp[i][0][1]) % P
    dp[i+1][1][0] =(dp[i+1][1][0] +  dp[i][1][0] * 25) % P
    if A[i+1] > 0:
        dp[i+1][1][1] =(dp[i+1][1][1] + dp[i][1][1]) % P
        dp[i+1][1][0] =(dp[i+1][1][0] + dp[i][1][1] * (A[i+1] - 1)) % P
ans = dp[N-1][1][0]
print(ans % P)