#include<iostream>
#include<string>
#include<algorithm>
#include<functional>
#include<vector>
#include<set>
#include<queue>
#include<list>
#include<stdio.h>
#include<stdlib.h>
#include<map>

using namespace std;

int main() {
	string input;
	cin >> input;
	
	string s;
	reverse_copy(input.begin(), input.end(), back_inserter(s));


	int ans = 0;
	int base = 0;
	for (int i = 0; i < s.length(); ++i) {
		if (s[i] == 'B') {
			ans += i - base;
			++base;
		}
	}

	cout << ans << endl;


	return 0;
}