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*Pairs and vectors can be used together to achieve some amazing results.* Here we will learn to use a vector that holds pairs.

You are given a **vector V of size n**. The vector hold pair of integers. Example V={(1,2),(3,4)...}. Now, you need to sum the second elements.

**Input Format:**

The first line of input contains **T** denoting the number of testcases. T testcases follow. Each testcase contains two lines of input. The first line contains n denoting the size of the array. The second line contains **2*n** elements.

**Output Format:**

For each testcase, in a new line, print the required output.

**Your Task:**

Since this is a function problem, you don't need to take any input. Just complete the provided function **sum()**.

**Constraints:**

1 <= T <= 100

1 <= n <= 10^{7}

0 <= V_{i }<= 10^{7}

**Examples:
Input:**

1

5

1 2 3 4 5 6 7 8 9 10

30

**Explanation:
Testcase1:**

v[0]= 1,2

v[1]= 3,4

v[2]= 5,6

v[3]= 7,8

v[4]= 9,10

Now we sum all the second elements of a pair. So 2+4+6+8+10=30

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