#include <bits/stdc++.h>

using namespace std;

int main(void) {
  string s;
  cin >> s;

  int cum = 0, ans = 0;
  for (int i = 0; i < s.size(); i++) {
    if (s[i] == 'B') continue;
    ans += i - cum++;
  }

  cout << ans << endl;

  return 0;
}