en2asc = lambda s: ord(s) - 97

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

p25 = [1] * N
for i in range(1, N):
    p25[i] = p25[i - 1] * 25 % MOD

ct_a = 0
ans = 0
for i, s in enumerate(S):
    a = en2asc(s)
    if a:
        # s != "a"
        if ct_a == 0:
            if i != N - 1:
                ans += (a - 1) * (N - i - 1) * p25[N - i - 2]
            ans += p25[N - i - 1]
        elif ct_a == 1:
            ans += (a - 1) * p25[N - i - 1]
        ans %= MOD
    else:
        # s == "a"
        ct_a += 1
        if ct_a > 1:
            break
print(ans)