#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <cstring>
#include <map>
#include <queue>
#include <cmath>

#define MOD 1000000007
#define ll long long
#define ld long double

using namespace std;


int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  string S;
  cin >> S;
  vector<ll> A;
  for(ll i =0;i<S.size();i++){
    if(S[i]=='A')A.push_back(i+1);
  }
  if(A.size()==0) cout << "0" << endl;
  else {
    ll re = (1+A.size())*A.size();
    re/=2;

    for(ll i =0;i<A.size();i++){
      re-=A[i];
    }
    cout << -re << endl;
  }

  return 0;
}