Missing Number

Missing Number

You are given all numbers between 1,2,…,n1,2,…,n except one. Your task is to find the missing number.

Input

The first input line contains an integer nn.

The second line contains n−1n−1 numbers. Each number is distinct and between 11 and nn (inclusive).

Output

Print the missing number.

Constraints

• 2≤n≤2⋅1052≤n≤2⋅105

Example

Input:
5
2 3 1 5

Output:
4

To solve this problem, you should aware of formula to sum 1 to n. Sum of n number is (n)(n+1) / 2.