#include <iostream>

using namespace std;

int main(void){
  int i, a, sum;
  char s[13];

  cin >> s;

  a = 0;
  sum = 0;
  
  for(i = 0; (i < 12) || (s[i] /= '\n'); ++i){
    if(s[i] == 'A'){
      sum += i - a;
      ++a;
    }
  }

  cout << sum << endl;
  
  return 0;
}