You are given a permutation (a sequence of N distinct integers between 1 and N) but exactly one integer is missing! Can you find this element?

Input

First line of the standard input contains a single integer N (2 <= N <= 100)

The second line contains N-1 integers. A permutation with one integer missing. All integers are between 1 and N and all of them are distinct.

Output

Output a single integer – the missing number from the permutation.

Example

Input:
10
10 2 3 1 9 7 8 6 4

Output:
5