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 $$$t$$$ ($$$1 \le t \le 10^5$$$). The description of the test cases follows.
The first line of each test case consists of two integers $$$n$$$ and $$$k$$$ ($$$1 \leq n,k \leq 2 \cdot 10^5$$$) — the length of $$$a$$$ and the number of days.
The following line of each test case consists of $$$n$$$ integers $$$a_1, a_2, \ldots, a_n$$$ ($$$1 \leq a_i \leq 10^9$$$) — the elements of array $$$a$$$.
It is guaranteed that:
- The sum of $$$n$$$ over all test cases won't exceed $$$2 \cdot 10^5$$$;
- The sum of $$$k$$$ over all test cases won't exceed $$$2 \cdot 10^5$$$;
- $$$a_1 < a_2 < \cdots < a_n$$$ 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 $$$\require{cancel}$$$ $$$\{\cancel 1, \cancel 2, 3, \cancel 4, \cancel 5, \cancel 6, 7, 8, 9, \ldots\} = \{3, 7, 8, 9, \ldots\}$$$. 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:
Day$$$S$$$ before$$$S$$$ after1$$$\{\cancel 1, 2, \cancel 3, 4, \cancel 5, \cancel 6, \cancel 7, 8, 9, 10, \ldots \}$$$$$$\to$$$$$$\{2, 4, 8, 9, 10, \ldots\}$$$2$$$\{\cancel 2, 4, \cancel 8, 9, \cancel{10}, \cancel{11}, \cancel{12}, 13, 14, 15, \ldots\}$$$$$$\to$$$$$$\{4, 9, 13, 14, 15, \ldots\}$$$3$$$\{\cancel 4, 9, \cancel{13}, 14, \cancel{15}, \cancel{16}, \cancel{17}, 18, 19, 20, \ldots\}$$$$$$\to$$$$$$\{9, 14, 18, 19, 20, \ldots\}$$$
The smallest element left after $$$k = 3$$$ days is $$$9$$$.