CF1867B.XOR Palindromes

传统题 时间 2000 ms 内存 256 MiB 5 尝试 1 已通过 1 标签

XOR Palindromes

You are given a binary string ss of length nn (a string that consists only of 00 and 11). A number xx is good if there exists a binary string ll of length nn, containing xx ones, such that if each symbol sis_i is replaced by silis_i \oplus l_i (where \oplus denotes the bitwise XOR operation), then the string ss becomes a palindrome.

You need to output a binary string tt of length n+1n+1, where tit_i (0in0 \leq i \leq n) is equal to 11 if number ii is good, and 00 otherwise.

A palindrome is a string that reads the same from left to right as from right to left. For example, 01010, 1111, 0110 are palindromes.

Input

Each test contains multiple test cases. The first line contains the number of test cases tt (1t1051 \le t \le 10^5). The description of the test cases follows.

The first line of each test case contains a single integer nn (1n1051 \le n \le 10^5).

The second line of each test case contains a binary string ss of length nn.

It is guaranteed that the sum of nn over all test cases does not exceed 10510^5.

Output

For each test case, output a single line containing a binary string tt of length n+1n+1 - the answer to the problem.

Note

Consider the first example.

  • t2=1t_2 = 1 because we can choose l=l = 010100, then the string ss becomes 111111, which is a palindrome.
  • t4=1t_4 = 1 because we can choose l=l = 101011.
  • It can be shown that for all other ii, there is no answer, so the remaining symbols are 00.

Samples

5
6
101011
5
00000
9
100100011
3
100
1
1
0010100
111111
0011111100
0110
11

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