Find the Missing Number in 0..n Using seen[]

Source: Phước Hưng OJ

Version: Phuoc Hung OJ Extended

Problem

You are given $n$ distinct integers $a_0,a_1,\ldots,a_{n-1}$ chosen from

Exactly one value $m\in U$ is missing. Find that value using presence marking.

Input

The first line contains $n$. The second line contains $n$ distinct integers with $0\le a_i\le n$.

Output

Print the unique missing integer $m$.

Subtask

Subtask 1 (20 points): $1\le n\le10$.

Subtask 2 (30 points): $1\le n\le5000$.

Subtask 3 (50 points): $1\le n\le2\cdot10^5$.

Example

Input

5
3 0 1 5 2

Output

4

Explanation

The result follows directly from the mathematical definition above.