Alternating Sum of Numbers
Description
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.
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 $t$ lines. For each test case, output the required alternating sum of the numbers.
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.
4
4
1 2 3 17
1
100
2
100 100
5
3 1 4 1 5
-15
100
0
10