MOD = 998244353

n = int(input())
S = input()
S = [ord(s) - 97 for s in S]

# dp[i][eq][a]
dp = [[[0] * 2 for _ in range(2)] for _ in range(n + 1)]
dp[0][1][0] = 1
for i, s in enumerate(S, 1):
    if s == 0:
        dp[i][0][1] = dp[i - 1][0][0] + dp[i - 1][0][1] * 25
        dp[i][1][1] = dp[i - 1][1][0]
    else:
        dp[i][0][0] = dp[i - 1][0][0] * 25 + dp[i - 1][1][0] * (s - 1)
        dp[i][0][1] = dp[i - 1][0][0] + dp[i - 1][0][1] * 25 + dp[i - 1][1][0] + dp[i - 1][1][1] * (s - 1)
        dp[i][1][0] = dp[i - 1][1][0]
        dp[i][1][1] = dp[i - 1][1][1]
    for j in range(2):
        for k in range(2):
            dp[i][j][k] %= MOD

print(dp[-1][0][1])