package no3458_scores_subSequence;
import java.util.*;
public class Main {
	static long MOD = 998244353;
	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int n = s.length();
		int M = 0;
		long ans = 0;
		for(int i = 0;i < n;i++) {
			if(s.charAt(i) == 'A') {
				ans += pow(3,M);
			}else {
				M++;
			}
		}System.out.println(ans % MOD);
	}static long pow(long a,long b) {
		long ret = 1;
		long v = a;
		while(b > 0) {
			if((b & 1) != 0) {
				ret = ret * v % MOD;
			}v = v * v % MOD;
			b >>= 1;
		}return ret;
	}

}