You are given a string S consisting only of the characters 'R' and 'W'.

In one operation, you may swap any two characters.

Determine the minimum number of swaps required to make all the 'R' characters appear consecutively.

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Input Format

• First line contains the string S.

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Output Format

Print the minimum number of swaps required.

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Constraints

• (1 <= |S|<= 2*10^5)

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Example 1

Input

WRRWRRW

Output

1

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Example 2

Input

RRRR

Output

0

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Example 3

Input

RWRWRW

Output

1

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Explanation

For "WRRWRRW":

There are 4 occurrences of 'R'.

Choose a window of length 4. The best window contains only one 'W', so only one swap is needed.