A. Alternating Sum of Numbers
time limit per test
2 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
You are given a sequence of integers. Output the alternating sum of this sequence. In other words, output a1−a2+a3−a4+a5−…
a
1
−
a
2
+
a
3
−
a
4
+
a
5
−
…
. That is, the signs of plus and minus alternate, starting with a plus.

Input
The first line of the test contains one integer t
t
 (1≤t≤1000
1
≤
t
≤
1000
) — the number of test cases. Then follow t
t
 test cases.

The first line of each test case contains one integer n
n
 (1≤n≤50
1
≤
n
≤
50
) — the length of the sequence. The second line of the test case contains n
n
 integers a1,a2,…,an
a
1
,
a
2
,
…
,
a
n
 (1≤ai≤100
1
≤
a
i
≤
100
).

Output
Output t
t
 lines. For each test case, output the required alternating sum of the numbers.

Example
Input
Copy
4
4
1 2 3 17
1
100
2
100 100
5
3 1 4 1 5
Output
Copy
-15
100
0
10
