## Lonely Integer

Consider an array of integers, , where all but one of the integers occur in pairs. In other words, every element in occurs exactly twice except for one unique element.

Given , find and print the unique element.

**Input Format**

The first line contains a single integer, , denoting the number of integers in the array.

The second line contains space-separated integers describing the respective values in .

**Constraints**

- It is guaranteed that is an odd number.
- , where .

**Output Format**

Print the unique number that occurs only once in on a new line.

**Sample Input 0**

```
1
1
```

**Sample Output 0**

```
1
```

**Explanation 0**

The array only contains a single , so we print as our answer.

**Sample Input 1**

```
3
1 1 2
```

**Sample Output 1**

```
2
```

**Explanation 1**

We have two 's and one . We print , because that's the only unique element in the array.

**Sample Input 2**

```
5
0 0 1 2 1
```

**Sample Output 2**

```
2
```

**Explanation 2**

We have two 's, two 's, and one . We print , because that's the only unique element in the array.