#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
string s;
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> s;
    int res = 0, cnt = 0;
    for (int i = s.size() - 1; i >= 1; i--)
        if (s[i] == 'B')
        {
            cnt++;
            res += abs(i - cnt);
        }
    cout << res;
}