CF1955E Long Inversions

给定一个长度为$ n $的01字符串$ s $。01字符串是指只包含字符'1' 和'0'的字符串 可以选定一个整数$ k $ ( $ 1 \le k \le n $ )，将字符串中的连续k个字符进行替换，将0替换成1，1替换成0。 当 $ n=5 $ , $ s=00100 $时 , 你可以指定$ k=3 $ ，做如下操作： - 翻转1-3的子串：$ s=\color{blue}{110}00 $ ; - 反转3-5的子串：$ s=11\color{blue}{111} $ ; 经过不限次操作后，寻找能将01字符串中的所有字符转换成1的最大$ k $值。

The first line contains an integer $ t $ ( $ 1 \le t \le 10^4 $ ) — the number of test cases. The first line of each test case contains an integer $ n $ ( $ 1 \le n \le 5000 $ ) — the length of the string $ s $ . The second line of each test case contains a string $ s $ of length $ n $ , consisting of the characters '1' and '0'. It is guaranteed that the sum of the values $ n^2 $ over all test cases in the test does not exceed $ 25 \cdot 10^6 $ .

For each test case, output the maximum integer $ k $ ( $ 1 \le k \le n $ ) for which it is possible to obtain a string $ s $ consisting only of the characters '1' using the described operations.