write a go solution for Description:
Ntarsis has been given a set S, initially containing integers 1,2,3,ldots,10^1000 in sorted order. Every day, he will remove the a_1-th, a_2-th, ldots, a_n-th smallest numbers in S simultaneously.

What is the smallest element in S after k days?

Input Format:
Each test contains multiple test cases. The first line contains the number of test cases t (1<=t<=10^5). The description of the test cases follows.

The first line of each test case consists of two integers n and k (1<=n,k<=2*10^5) — the length of a and the number of days.

The following line of each test case consists of n integers a_1,a_2,ldots,a_n (1<=a_i<=10^9) — the elements of array a.

It is guaranteed that:

- The sum of n over all test cases won't exceed 2*10^5;
- The sum of k over all test cases won't exceed 2*10^5;
- a_1<a_2<*s<a_n for all test cases.

Output Format:
For each test case, print an integer that is the smallest element in S after k days.

Note:
For the first test case, each day the 1-st, 2-nd, 4-th, 5-th, and 6-th smallest elements need to be removed from S. So after the first day, S will become requirecancel cancel1,cancel2,3,cancel4,cancel5,cancel6,7,8,9,ldots=3,7,8,9,ldots. The smallest element is 3.

For the second case, each day the 1-st, 3-rd, 5-th, 6-th and 7-th smallest elements need to be removed from S. S will be changed as follows:

DayS beforeS after1cancel1,2,cancel3,4,cancel5,cancel6,cancel7,8,9,10,ldotsto2,4,8,9,10,ldots2cancel2,4,cancel8,9,cancel10,cancel11,cancel12,13,14,15,ldotsto4,9,13,14,15,ldots3cancel4,9,cancel13,14,cancel15,cancel16,cancel17,18,19,20,ldotsto9,14,18,19,20,ldots

The smallest element left after k=3 days is 9.. Output only the code with no comments, explanation, or additional text.