Question
The Missing Book Number
A teacher numbered KaTeX can only parse string typed expression books from KaTeX can only parse string typed expression to KaTeX can only parse string typed expression and placed them on a shelf. Later, she noticed that only KaTeX can only parse string typed expression books were present and exactly one book was missing. You are given the numbers written on the remaining books. Your task is to find the missing book number.
Input
The first line contains a single integer KaTeX can only parse string typed expression — the number of books currently on the shelf.
The second line contains KaTeX can only parse string typed expression natural numbers — KaTeX can only parse string typed expression, representing the numbers on the remaining books.
The second line contains KaTeX can only parse string typed expression natural numbers — KaTeX can only parse string typed expression, representing the numbers on the remaining books.
Output
Print a single integer — the number of the missing book.
Example
Input
5
1 2 4 5 6
Output
3
Explanation
The books should be numbered from KaTeX can only parse string typed expression to KaTeX can only parse string typed expression.
The book numbered KaTeX can only parse string typed expression is missing.
5
1 2 4 5 6
Output
3
Explanation
The books should be numbered from KaTeX can only parse string typed expression to KaTeX can only parse string typed expression.
The book numbered KaTeX can only parse string typed expression is missing.