#include <iostream>
#include <string>

using namespace std;

string s;

int main() {
  cin >> s;

  int counter = 0;
  for (int i = s.size() - 1; i <= 0; i--) {
    if (s[i] == 'B') {
      counter += s.size() - 1 - i;
    }
  }
  cout << counter << endl;
}