N = int(input())
S = input()
MOD = 998244353

dp = [[0]*2 for _ in range(N+1)]
dp[0] = [0, 0]
cta = 0
for i in range(N):
    s = S[i]
    ind = ord(s)-97
    dp[i+1][0] = 25*dp[i][0] % MOD
    dp[i+1][1] = dp[i][1]*25 % MOD
    dp[i+1][1] += dp[i][0]
    dp[i+1][1] %= MOD
    if cta < 2:
        dp[i+1][cta] += max(0, ind-1)
        dp[i+1][cta] %= MOD
        if ind and cta == 0:
            dp[i+1][1] += 1
            dp[i+1][1] %= MOD
    if ind == 0:
        cta += 1

print(dp[N][1])