Missing Number
You are given all numbers between 1,2,\ldots,n except one. Your task is to find the missing number.
Input
The first input line contains an integer n.
The second line contains n-1 numbers. Each number is distinct and between 1 and n (inclusive).
Output
Print the missing number.
Constraints
2 \le n \le 2 \cdot 10^5
Example
Input:
5
2 3 1 5
Output:
4
- XOR Sum
- a xor a = 0
- init xor_sum = 0
- xor all input
- xor all 1..=n
- xor_sum = missing