#include "bits/stdc++.h"

using namespace std;


static long long dp[3] = {0, 1};

static void solve()
{
  string str;
  cin >> str;
  int ans = 0, n = count(str.begin(), str.end(), 'A');
  auto p = str.begin();
  string searchstr = "A";
  for(int i = 0; i < n; i++) {
    p = find_first_of(p, str.end(), searchstr.begin(), searchstr.end());
    ans += p - str.begin() - i;
    p++;
  }
  cout << ans << "\n";
}

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