using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using System.Text;
//using static CompLib.CompLib;
//using DataStructure;

namespace atcoder
{
    class Program
    {
        const int intMax = 1000000000;
        const long longMax = 2000000000000000000;
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            String S = Console.ReadLine();
            long mod = 998244353;
            var list = new List<int>();
            int cnt = 0;
            for (int i = 0; i < N; i++)
            {
                if (S[i] == 'A' || S[i] == 'B') cnt++;
            }
            var comb = new Comb(N, mod);
            long ans = comb.nCk(N, cnt);
            Console.WriteLine(ans);
        }
    }
    public class Comb
    {
        private long[] fact_;
        private long[] fact_inv_;
        private long[] inv_;
        private long mod = 1000000007;

        public Comb(int SIZE, long mod = 1000000007)
        {
            this.mod = mod;
            fact_ = Enumerable.Repeat((long)1, SIZE + 1).ToArray();
            fact_inv_ = Enumerable.Repeat((long)1, SIZE + 1).ToArray();
            inv_ = Enumerable.Repeat((long)1, SIZE + 1).ToArray();
            for (int i = 2; i < SIZE + 1; i++)
            {
                fact_[i] = fact_[i - 1] * i % mod;
                inv_[i] = mod - inv_[mod % i] * (mod / i) % mod;
                fact_inv_[i] = fact_inv_[i - 1] * inv_[i] % mod;
            }
        }
        public long nCk(int n, int k)
        {
            return fact_[n] * (fact_inv_[k] * fact_inv_[n - k] % mod) % mod;
        }
        public long nHk(int n, int k)
        {
            return nCk(n + k - 1, k);
        }
        public long fact(int n)
        {
            return fact_[n];
        }
        public long fact_inv(int n)
        {
            return fact_inv_[n];
        }
        public long inv(int n)
        {
            return inv_[n];
        }
    }
}