There are N cubes stacked vertically on a desk. You are given a string S of length N . The color of the i -th cube from the bottom is red if the i -th character in S is 0 , and blue if that character is 1 .
You can perform the following operation any number of times: choose a red cube and a blue cube that are adjacent, and remove them. Here, the cubes that were stacked on the removed cubes will fall down onto the object below them.
What is the maximum number of cubes that can be removed?
Input
The input contains one line with the string
Output
Print the maximum number of cubes that can be removed.
Sample test(s)
Input
0011
Output
4
Input
11011010001011
Output
12
Input
0
Output
0