import java.io.*;
import java.util.*;

public class Main {
    static final int MOD = 998244353;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int ab = 0;
        for (char c : sc.next().toCharArray()) {
            if (c == 'A' || c == 'B') {
                ab++;
            }
        }
        System.out.println(getComb(n, ab));
    }
    
    static long getComb(long n, long r) {
        if (n - r < r) {
            return getComb(n, n - r);
        }
        long ans = 1;
        long div = 1;
        for (int i = 1; i <= r; i++) {
            ans *= n - i + 1;
            ans %= MOD;
            div *= i;
            div %= MOD;
        }
        return ans * pow(div, MOD - 2) % MOD;
    }
    
    static long pow(long x, int p) {
        if (p == 0) {
            return 1;
        } else if (p % 2 == 0) {
            return pow(x * x % MOD, p / 2);
        } else {
            return pow(x, p - 1) * x % MOD;
        }
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}