MOD = 998244353

fact_range = 10**6
fact = [1] * (fact_range + 1)
for i in range(0, fact_range):
    fact[i+1] = fact[i] * (i + 1) % MOD

ifact = [1] * (fact_range + 1)
ifact[fact_range] = pow(fact[fact_range], MOD - 2, MOD)
for i in range(fact_range, 0, -1):
    ifact[i-1] = ifact[i] * i % MOD

def comb(n, k):
    if k < 0 or n < k:
        return 0
    else:
        return fact[n] * ifact[n-k] % MOD * ifact[k] % MOD


n = int(input())
s = input()
ok = False
for t in 'ABC', 'BCA', 'CAB':
    i = 0
    for c in s:
        if c == t[i]:
            i += 1
            if i == 3:
                ok = True
                break
if not ok:
    print(1)
    exit()
ca, cb, cc = map(s.count, 'ABC')
ans = (fact[n] * ifact[ca] * ifact[cb] * ifact[cc] - ca - cb - cc) % MOD
print(ans)