#include <iostream>
#include <string>
using namespace std;
int main(void){
    int n=0,i=0,b=0;
    string s;
    cin>>s;
    for(auto c : s){
        if(c=='B'){
            n+=i;
            b++;
        }
        i++;
            
    }
    cout<<n-b*(b-1)/2;
}