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Problem of the day

You have been given an integer array/list(ARR) of size N. Where N is equal to [2M + 1].

Now, in the given array/list, 'M' numbers are present twice and one number is present only once.

You need to find and return that number which is unique in the array/list.

```
Unique element is always present in the array/list according to the given condition.
```

Detailed explanation

```
1 <= t <= 10^2
0 <= N <= 10^3
Time Limit: 1 sec
```

```
1
7
2 3 1 6 3 6 2
```

```
1
Explanation: The array is [2, 3, 1, 6, 3, 6, 2]. Here, the numbers 2, 3, and 6 are present twice, and the number 1 is present only once. So, the unique number in this array is 1.
```

```
2
5
2 4 7 2 7
9
1 3 1 3 6 6 7 10 7
```

```
4
Explanation: In the first test case, the array is [2, 4, 7, 2, 7]. Here, the numbers 2 and 7 are present twice, and the number 4 is present only once. So, the unique number in this array is 4.
10
Explanation: In the second test case, the array is [1, 3, 1, 3, 6, 6, 7, 10, 7]. Here, the numbers 1, 3, 6, and 7 are present twice, and the number 10 is present only once. So, the unique number in this array is 10.
```