Find the Missing Positive Integer

Given an unsorted list of integers, your task is to find the smallest positive integer (greater than 0) that is missing from the list.

Note: The solution should work efficiently in O(n) time with constant extra space. The input will be read from stdin and the output should be printed to stdout.

Example: For the input 3 4 -1 1 (with array size provided), the missing positive integer is 2, since 1 is present and 2 is the smallest number greater than 0 that is absent.

inputFormat

The first line of input contains a single integer n that denotes the size of the array. If n is 0, the array is empty. The second line contains n space-separated integers representing the elements of the array.

outputFormat

Output a single integer representing the smallest missing positive integer.

## sample

4
3 4 -1 1

2

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