#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

string s;
int a = 0;
int main(){
	cin >> s;
	for (int i = 0; i <= s.length() - 1; i++) {
		if (s[i] == 'A') a++;
	}
	int latter = (1 + a)*a / 2;
	int former = 0;
	for (int i = 0; i <= s.length() - 1; i++) {
		if (s[i] == 'A') former += i + 1;
	}
	cout << former - latter << endl;
	return 0;
}