#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
int main() {
  string S; cin >> S;
  int a = 0;
  int b = 0;
  int ans = 0;
  for(int i = 0; i < S.size(); i++) {
    if('A' == S[i]) {
      ans += i - a;
      a++;
    }
  }
  cout << ans << endl;
  
}