#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int main() {
    string s;
    cin >> s;
    int ans = 0;
    int b = 0;
    for (char c : s) {
        if (c == 'B') b++;
        else ans += b;
    }
    cout << ans << endl;
    return 0;
}