codeforce 556A

题目

                       A. Case of the Zeros and Ones

Andrewid the Android is a galaxy-famous detective. In his free time he
likes to think about strings containing zeros and ones.

Once he thought about a string of length n consisting of zeroes and
ones. Consider the following operation: we choose any two adjacent
positions in the string, and if one them contains 0, and the other
contains 1, then we are allowed to remove these two digits from the
string, obtaining a string of length n - 2 as a result.

Now Andreid thinks about what is the minimum length of the string that
can remain after applying the described operation several times
(possibly, zero)? Help him to calculate this number.

Input First line of the input contains a single integer n
(1 ≤ n ≤ 2·105), the length of the string that Andreid has.

The second line contains the string of length n consisting only from
zeros and ones.

Output Output the minimum length of the string that may remain after
applying the described operations several times.

Sample test(s) input 4 1100 output 0 input 5 01010 output 1 input 8
11101111 output 6 Note In the first sample test it is possible to
change the string like the following: .

In the second sample test it is possible to change the string like the
following: .

In the third sample test it is possible to change the string like the
following:

题意

给予一个字符串字符串中 01 或10 可以相互抵消
抵消之后消失
后面的字符串自动跟上
可以继续抵消前面的
直至1 或 0 消失为止

技巧

用1的个数减去0的个数取绝对值就是剩余数字的个数 - -

当初我的智商呢？？？？？？？？？？？？？？？？？？

实现方法

略