#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sstream>
#include <iostream>
#include <math.h>
#include <time.h>
#include <unistd.h>
#include <algorithm>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <set>
#include <string>

#ifndef ONLINE_JUDGE
	#define DEBUG(x) cout << '>' << #x << ':' << x << endl;
#else
	#define DEBUG(x) do {} while(0);
#endif

#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define FOR(i, A, N) for(int (i) = (A); (i) < (N); (i)++)
#define REP(i, N) for(int (i) = 0; (i) < (N); (i)++)

using namespace std;
typedef long long ll;
inline bool EQ(double a, double b) { return fabs(a-b) < 1e-9; }
typedef int oint;
#define int long long

int n,m;
char str[555555];
int x[555555];


int _mergeSort(int arr[], int temp[], int left, int right); 
int merge(int arr[], int temp[], int left, int mid, int right); 
  
/* This function sorts the input array and returns the 
   number of inversions in the array */
int mergeSort(int arr[], int array_size) 
{ 
    int* temp = (int*)malloc(sizeof(int) * array_size); 
    return _mergeSort(arr, temp, 0, array_size - 1); 
} 
  
/* An auxiliary recursive function that sorts the input array and 
  returns the number of inversions in the array. */
int _mergeSort(int arr[], int temp[], int left, int right) 
{ 
    int mid, inv_count = 0; 
    if (right > left) { 
        /* Divide the array into two parts and call _mergeSortAndCountInv() 
       for each of the parts */
        mid = (right + left) / 2; 
  
        /* Inversion count will be sum of inversions in left-part, right-part 
      and number of inversions in merging */
        inv_count = _mergeSort(arr, temp, left, mid); 
        inv_count += _mergeSort(arr, temp, mid + 1, right); 
  
        /*Merge the two parts*/
        inv_count += merge(arr, temp, left, mid + 1, right); 
    } 
    return inv_count; 
} 
  
/* This funt merges two sorted arrays and returns inversion count in 
   the arrays.*/
int merge(int arr[], int temp[], int left, int mid, int right) 
{ 
    int i, j, k; 
    int inv_count = 0; 
  
    i = left; /* i is index for left subarray*/
    j = mid; /* j is index for right subarray*/
    k = left; /* k is index for resultant merged subarray*/
    while ((i <= mid - 1) && (j <= right)) { 
        if (arr[i] <= arr[j]) { 
            temp[k++] = arr[i++]; 
        } 
        else { 
            temp[k++] = arr[j++]; 
  
            /*this is tricky -- see above explanation/diagram for merge()*/
            inv_count = inv_count + (mid - i); 
        } 
    } 
  
    /* Copy the remaining elements of left subarray 
   (if there are any) to temp*/
    while (i <= mid - 1) 
        temp[k++] = arr[i++]; 
  
    /* Copy the remaining elements of right subarray 
   (if there are any) to temp*/
    while (j <= right) 
        temp[k++] = arr[j++]; 
  
    /*Copy back the merged elements to original array*/
    for (i = left; i <= right; i++) 
        arr[i] = temp[i]; 
  
    return inv_count; 
} 

oint main() {
	scanf("%s", str);
	n = strlen(str);
	REP(i, n) x[i] = (str[i] == 'B') ? 1 : 0;
	printf("%lld\n", mergeSort(x, n));
	return 0;
}


Measured memory_bytes: 3584