B"A binary string is a string where each character is either 0 or 1. Two binary strings a and b of equal length are similar, if they have the same character in some position (there exists an integer i such that a_i = b_i ). For example: You are given an integer n and a binary string s consisting of 2n-1 characters. Let's denote s[l..r] as the contiguous substring of s starting with l -th character and ending with r -th character (in other words, s[l..r] = s_l s_{l + 1} s_{l + 2} ... s_r ). You have to construct a binary string w of length n which is similar to all of the following strings: s[1..n] , s[2..n+1] , s[3..n+2] , ..., s[n..2n-1] . The first line contains a single integer t ( 1 <= t <= 1000 ) -- the number of test cases. The first line of each test case contains a single integer n ( 1 <= n <= 50 ). The second line of each test case contains the binary string s of length 2n - 1 . Each character s_i is either 0 or 1. For each test case, print the corresponding binary string w of length n . If there are multiple such strings -- print any of them. It can be shown that at least one string w meeting the constraints always exists. The explanation of the sample case (equal characters in equal positions are bold): The first test case: The second test case: The third test case: The fourth test case: "...