#include <bits/stdc++.h>
#define REP(i,n,N) for(int i=(n);i<(int) N;i++)
#define RREP(i,n,N) for(int i=N-1;i>=(int) n;i--)
#define p(s) cout<<(s)<<endl
#define DEBUG(x,y) cout<<#x<<": "<<x<<" , "<<#y<<": "<<y<<endl;
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define F first
#define S second
typedef long long ll;
using namespace std;
const ll mod=1e9+7;

int main(){
	string s;
	cin>>s;
	int n=s.size(),ans=0;
	int cnt=0;
	RREP(i,0,n){
		if(s[i]=='B'){
			ans+=cnt;
		}else{
			cnt++;
		}
	}
	p(ans);
	return 0;
}