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 format:
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 format:
Output $$$t$$$ lines. For each test case, output the required alternating sum of the numbers.
Example Input 0:
4
4
1 2 3 17
1
100
2
100 100
5
3 1 4 1 5

Example Output 0:
-15
100
0
10



Example input:
4
4
1 2 3 17
1
100
2
100 100
5
3 1 4 1 5


Example output:
-15
100
0
10