Missing Number

Source: CSES

Version: Phuoc Hung OJ Extended

Problem

You are given an integer $n$. Exactly one number from $1,2,\ldots,n$ is missing. The input contains the other $n-1$ pairwise distinct numbers.

Find the missing number.

For Chapter 32, the primary solution uses a presence array: mark every value that appears, then find the unmarked value.

Input

• The first line contains $n$.
• The second line contains $n-1$ pairwise distinct integers from $[1,n]$.

Output

Print the unique missing number.

Subtasks

Subtask 1 (20 points): $2\le n\le 20$; the given $n-1$ numbers are pairwise distinct and lie in $[1,n]$.

Subtask 2 (30 points): $2\le n\le 2000$; the given $n-1$ numbers are pairwise distinct and lie in $[1,n]$.

Subtask 3 (50 points): $2\le n\le 200000$; the given $n-1$ numbers are pairwise distinct and lie in $[1,n]$.

Example

Input

5
2 3 1 5

Output

4

Explanation

Among {1,2,3,4,5}, only 4 is absent.