N = int(input())
S = input()
mod = 998244353
# dp[i][j] i個目まで見て(j=0未満未確定,j=1未満確定,j=2 aが一つ未満未確定,j=3 aが一つ未満確定)
dp = [[0]*(4) for i in range(N+1)]
dp[0][0] = 1
a0 = ord('a')
for i in range(N):
    ord_s = ord(S[i])-a0
    if ord_s == 0:
        dp[i+1][2] += dp[i][0]
        dp[i+1][1] += dp[i][1]*25
        dp[i+1][3] += dp[i][1]
    else:
        dp[i+1][0] += dp[i][0]
        dp[i+1][1] += dp[i][0]*(ord_s-1)+dp[i][1]*25
        dp[i+1][3] += dp[i][0] + dp[i][1] + dp[i][2]*(ord_s-1)+dp[i][3]*25
        dp[i+1][2] += dp[i][2]
    dp[i+1][0] %= mod
    dp[i+1][1] %= mod
    dp[i+1][2] %= mod
    dp[i+1][3] %= mod
print(dp[-1][3])