n = int(input())
s = input()
dp = [[[0 for _ in range(2)] for __ in range(2)] for ___ in range(n+1)]
dp[0][0][0] = 1
mod = 998244353
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("a") + ord(s[i])
    for j in range(now):
        if j == 0:
            dp[i+1][1][1] += dp[i][0][0]
        else:
            dp[i+1][0][1] += dp[i][0][0]
            dp[i+1][1][1] += dp[i][1][0]
    if now == 0:
        dp[i+1][1][0] += dp[i][0][0]
    else:
        dp[i+1][0][0] += dp[i][0][0]
        dp[i+1][1][0] += dp[i][1][0]
    dp[i+1][0][0] %= mod
    dp[i+1][0][1] %= mod
    dp[i+1][1][0] %= mod
    dp[i+1][1][1] %= mod
#     print(dp)
print(dp[n][1][1])