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 Si​=B, the $i$-th piece from the left is showing black; If Si​=W, the $i$-th piece from the left is showing white.

Consider performing the following operation:

• Choose $i$ ($1\le i<N$) 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≤∣S∣≤2×105
• Si​=B or W

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