**Definitions**
Let $ t \in \mathbb{Z} $ be the number of test cases.
Let $ T = \{(n_k, A_k) \mid k \in \{1, \dots, t\}\} $ be the set of test cases, where for each $ k $:
- $ n_k \in \mathbb{Z} $ denotes the length of the sequence.
- $ A_k = (a_{k,1}, a_{k,2}, \dots, a_{k,n_k}) $ is a sequence of integers.
**Constraints**
1. $ 1 \le t \le 1000 $
2. For each $ k \in \{1, \dots, t\} $:
- $ 1 \le n_k \le 50 $
- $ 1 \le a_{k,i} \le 100 $ for all $ i \in \{1, \dots, n_k\} $
**Objective**
For each test case $ k \in \{1, \dots, t\} $, compute:
$$ S_k = \sum_{i=1}^{n_k} (-1)^{i-1} a_{k,i} $$