Description

Class is about to begin, and the teacher notices that one student is missing.
There are $n$ students in total, with student IDs ranging from $1$ to $n$. The teacher records the IDs of all present students. Help the teacher write a program to find the ID of the missing student.

Input Format

The first line contains $n$, the total number of students who should be present ($1 < n < 10^6$).
This is followed by $n-1$ lines, each containing an integer representing the ID of a present student (it is guaranteed that no student ID appears twice).

Output Format

Output a single integer representing the ID of the missing student.

Sample

3
1
3

2