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B. Balanced Substring

time limit per test

1 secondmemory limit per test

256 megabytesinput

standard inputoutput

standard outputYou are given a string *s* consisting only of characters 0 and 1. A substring [*l*, *r*] of *s* is a string *s*_{l}*s*_{l + 1}*s*_{l + 2}... *s*_{r}, and its length equals to *r* - *l* + 1. A substring is called balanced if the number of zeroes (0) equals to the number of ones in this substring.

You have to determine the length of the longest balanced substring of *s*.

Input

The first line contains *n* (1 ≤ *n* ≤ 100000) — the number of characters in *s*.

The second line contains a string *s* consisting of exactly *n* characters. Only characters 0 and 1 can appear in *s*.

Output

If there is no non-empty balanced substring in *s*, print 0. Otherwise, print the length of the longest balanced substring.

Examples

Input

8

11010111

Output

4

Input

3

111

Output

0

Note

In the first example you can choose the substring [3, 6]. It is balanced, and its length is 4. Choosing the substring [2, 5] is also possible.

In the second example it's impossible to find a non-empty balanced substring.

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

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