Catch Rock If You Can (April Fools Series)
Rock is a wanted criminal. He is now hiding somewhere. Your task is to inspect this page and find Rock for confession!
Input
The first line of the input consists of a single integer $N$. $(1 \le N \le 100000)$.
The second line of the input consists of $N$ positive integers $D$. $(1 \le D \le 100000)$.
Output
Output an integer.
Sample Test Cases
| Input | Output | |
|---|---|---|
| 5 1 2 3 4 5 |
6 | |
| 4 2 3 2 3 |
4 |
Scoring: Per Subtask
Authored by hclee
Appeared in 中國香港九龍華仁書院電腦科主任李海峻老師精心調製之全校青少年信息學奧林匹克六月愚人節編程競賽