Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.
You are given a sequence of integers. Output the alternating sum of this sequence. In other words, output $$$a_1 - a_2 + a_3 - a_4 + a_5 - \dots$$$. That is, the signs of plus and minus alternate, starting with a plus.
Input
The first line of the test contains one integer $$$t$$$ ($$$1 \le t \le 1000$$$) — the number of test cases. Then follow $$$t$$$ test cases.
The first line of each test case contains one integer $$$n$$$ ($$$1 \le n \le 50$$$) — the length of the sequence. The second line of the test case contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$1 \le a_i \le 100$$$).
Output
Output $$$t$$$ lines. For each test case, output the required alternating sum of the numbers.