Find a Peak Element

You are given an array of integers. A peak element is defined as an element that is strictly greater than its immediate neighbors. If the array is empty, the answer is defined as -1, and if there is only one element, that element is considered a peak.

Your task is to find any peak element from the array using an algorithm with time complexity better than O(n), hinting at a binary search approach.

Note: It is guaranteed that the input will be given in the following format: the first number is an integer n representing the number of elements in the array. If n > 0, the next line contains n space-separated integers. Use standard input (stdin) for reading input and standard output (stdout) for printing the result.

For example:

Input:
6
1 3 20 4 1 0
Output:
20

</p>

inputFormat

The first line contains a single integer n (n ≥ 0), which is the number of elements in the list. If n > 0, the second line contains n space-separated integers representing the array elements.

outputFormat

Print a single integer – one peak element from the array. If the list is empty, print -1.

## sample

6
1 3 20 4 1 0

20