CF556A.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.

安卓侦探安德鲁伊德是银河系闻名的侦探。闲暇时，他喜欢思考由 0 和 1 组成的字符串。

某次，他考虑了一个长度为 $n$、仅由 0 和 1 构成的字符串。考虑如下操作：我们任选字符串中两个相邻的位置，若其中一个位置为 0、另一个位置为 1，则允许将这两个数字从字符串中移除，从而得到一个长度为 $n-2$ 的新字符串。

现在安德鲁伊德在思考：对原字符串反复执行上述操作（次数可以为零次）后，所能得到的字符串的最小可能长度是多少？请帮助他计算这个数值。

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.

输入的第一行包含一个整数 $n$（$1 ≤ n ≤ 2·10^5$），表示安德烈德所拥有的字符串的长度。

第二行包含一个长度为 $n$ 的字符串，仅由字符 0 和 1 组成。

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

输出在多次执行上述操作后，字符串可能的最短长度。

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: .

在第一个样例测试中，可以按如下方式修改字符串：。

在第二个样例测试中，可以按如下方式修改字符串：。

在第三个样例测试中，可以按如下方式修改字符串：。