ENG  RUS Timus Online Judge
Online Judge
Problems
Authors
Online contests
Site news
Webboard
Problem set
Submit solution
Judge status
Guide
Register
Authors ranklist
Current contest
Scheduled contests
Past contests
Rules

## 1395. Pascal vs. C++. Version 2

Time limit: 1.0 second
Memory limit: 4 MB
Language limit: C, C++, Pascal

### Background

This problem is a hardcore version of the problem "Pascal vs. C++". We, Timus Top Coders, dedicate it to those, who still believe in the power of human intellect. In the fact, that there is no limit to perfection. In the fact, that all the languages are equal. In the freedom of choice. In the unlimited programming! We are happy we could create this problem. And we hope you will be proud after you solve it. Enjoy!

### Problem

A sequence S consists of N elements S[i] indexed from 1 to N. You should take a maximal number of different elements from this sequence which are successive terms of some increasing arithmetical progression. The order of these elements in the sequence S does not matter. And may Pascal, C++ and Java be with you ;)

### Input

The first line contains the integer number N (2 ≤ N ≤ 10000). The second line contains N integers S[i] (1 ≤ S[i] ≤ 109).

### Output

The first line should contain the maximal number of taken elements. The second line should contain the indexes of these elements in the sequence S. The indexes may be listed in any order and should be separated by single spaces. If the problem has several solutions, you should output any of them.

inputoutput
```6
7 3 2 3 5 9
```
```4
4 5 1 6
```

### Notes

We recommend you to solve this problem on C++, because in this specific case local C++ compiler produces more effective binaries than Pascal and Java compilers.
Problem Author: Ilya Grebnov, Dmitry Kovalioff, Nikita Rybak
Problem Source: Timus Top Coders: Second Challenge