minions-sequence
Source: hackerearth
Difficulty: MEDIUM

Gru and minions are playing with numbers. Gru gives a list of numbers to a minion and asks him to tell the minimum possible last number of a non decreasing sequence of length L.

Input: Input consists of number of test cases T. Each test case contains size of array i.e N. Next line contains N space separated elements of array. Next line contains length of the non decreasing sequence i.e. L.

Output: You have to print the minimum possible last number of a sequence and if their is no non-decreasing sequence of length L, then print "-1" without the quotes.

Constraints:    1 ≤ T ≤ 100   |   1 ≤ N ≤ 106   |   1 ≤ a[i] ≤ 106   |   1 ≤ L ≤ N

SAMPLE INPUT
1
7
9 7 2 5 4 11 12 
3

SAMPLE OUTPUT
11

Explanation

In sample input, possible non-decreasing sequences of length L=3 are
(9,11,12) , (7,11,12) , (2,5,11) , (2,4,11) , (2,5,12) , (2,4,12) , (2,11,12) , (5,11,12) , (4,11,12)
and the minimum last number is 11 for the sequences (2,5,11) and (2,4,11). Hence, the answer is 11.