Missing Picture Identifier

You are given a total number of pictures n that were originally labeled from 1 to n. However, one picture identifier is missing. You are provided with the list of the remaining n-1 identifiers (in any order). Your task is to determine the missing picture identifier.

Note that the sum of the first n natural numbers is given by the formula: \( \frac{n(n+1)}{2} \).

Example:

Input:
5
1 2 4 5
Output:
3

</p>

inputFormat

The first line of input contains an integer n (the total number of pictures). The second line contains n-1 space-separated integers representing the identifiers of the remaining pictures.

outputFormat

Output a single integer – the missing picture identifier.

## sample

5
1 2 4 5

3