Missing Number

Source: CSES

Version: Phuoc Hung OJ Extended

Problem Statement

All numbers from 1 through n except exactly one are given. The n-1 supplied numbers are distinct and within [1,n]. Find the missing number.

Input

First line: n (2<=n<=200000). Second line: n-1 distinct integers in [1,n].

Output

Print the missing integer.

Subtasks

• Subtask 1 (20%): $2\le n\le10$.
• Subtask 2 (30%): $2\le n\le1000$.
• Subtask 3 (50%): $2\le n\le200000$ (đầy đủ miền CSES).

Examples

Example 1

Input:

5
2 3 1 5

Output:

4

Explanation:

The full sum is 15; the given numbers sum to 11, so the missing number is 4.

Example 2

Input:

2
2

Output:

1

Explanation:

Only 2 is given, so 1 is missing.