#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <iomanip>
#include <string>
#include <cmath>
#include <vector>
#include <algorithm>
#include <queue>
#include <functional>
#include <map>


using namespace std;

#define MOD 1000000007
#define INF 2147483647
#define ll long long


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

	vector<int> B;
	for (int i = s.size() - 1; i >= 0; i--) {
		if (s[i] == 'B') {
			B.push_back(s.size() - i - 1);
		}
	}
	int cnt = 0;
	int res = 0;
	for (int i = 0; i < B.size(); i++) {
		res += B[i] - cnt;
		cnt++;
	}

	cout << res << endl;

	return (0);
}