Score : 300 points

Problem Statement

There are N Reversi pieces arranged in a row. (A Reversi piece is a disc with a black side and a white side.) The state of each piece is represented by a string S of length N. If S_i=B, the i-th piece from the left is showing black; If S_i=W, the i-th piece from the left is showing white.

Consider performing the following operation:

  • Choose i (1 \leq i < N) such that the i-th piece from the left is showing black and the (i+1)-th piece from the left is showing white, then flip both of those pieces. That is, the i-th piece from the left is now showing white and the (i+1)-th piece from the left is now showing black.

Find the maximum possible number of times this operation can be performed.

Constraints

  • 1 \leq |S| \leq 2\times 10^5
  • S_i=B or W

Input

Input is given from Standard Input in the following format:

S

Output

Print the maximum possible number of times the operation can be performed.


Sample Input 1

BBW

Sample Output 1

2

The operation can be performed twice, as follows:

  • Flip the second and third pieces from the left.
  • Flip the first and second pieces from the left.

Sample Input 2

BWBWBW

Sample Output 2

6