Given an increasing sequence a[], we need to find the K-th missing contiguous element in the increasing sequence which is not present in the sequence. If no k-th missing element is there output -1.

Input:
The first line consists of an integer T i.e. the number of test cases. The first line of each test case consists of two integers N and K.Next line consists of N spaced integers.

Output:
For each test case, print the Kth missing number if present otherwise print -1.

Explanation:
#TestCase 1: K=2
We need to find the 2nd missing number in the array. Missing numbers are 2 and 6. So 2nd missing number is 6. #Testcase 2:
K=2
We need to find the 2nd missing number in the array. As there is no missing number, hence the output is -1.