Lexicographically Smallest Binary String

You are given a binary string of length N. In one operation, you can perform certain transformations on the string (the details of these operations are omitted here, but it is guaranteed that applying them sufficiently many times can always yield the lexicographically smallest string possible).

Your task is to compute the lexicographically smallest binary string that can be obtained from the given binary string. It turns out that the answer is always a string consisting entirely of zeros of length N (i.e. $$0^N$$).

Example:

• For \(N = 3\) and binary string "101", the answer is "000".
• For \(N = 5\) and binary string "11001", the answer is "00000".

inputFormat

The first line contains an integer T representing the number of test cases. Each of the next T lines contains a test case. Each test case is described by an integer N and a binary string of length N separated by a space.

outputFormat

For each test case, output the lexicographically smallest binary string (which is simply a string of N zeros) on a separate line.

## sample

1
3 101

000

</p>