import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

class Main {

    public static void main(String[] args) {
        new Main().compute();
    }

    void compute() {
        Scanner sc = new Scanner(System.in);
        String S = sc.next();
        List<Character> SList = new ArrayList<>();
        for (int i = 0; i < S.length(); i++) {
            SList.add(S.charAt(i));
        }
        int ans = 0;
        while (SList.contains('A')) {
            ans += SList.indexOf('A');
            SList.remove(new Character('A'));
        }
        System.out.println(ans);
    }
}