#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 n = s.size();
    int res = 0, tmp = 0, cnt = 0;
    for (int i = n - 1; i >= 0; i--)
        if (s[i] == 'B')
        {
            tmp = i;
            break;
        }
    for (int i = tmp; i >= 0; i--)
        if (s[i] == 'B')
        {
            res += (tmp - i - cnt);
            cnt++;
        }
    cout << res;
}