# 1159 : Average of Two Numbers

Time Limit: 1 Sec Memory Limit: 128 Mb Submitted: 1235 Solved: 424## Description

Given a list of *n* different numbers, which number in this list can be represented as an average of any two other numbers in the same list?

## Input

There are multiple test cases.

The first line of each test case is an integer *n*, where 3 ≤ *n* ≤ 1000. The second line contains *n* different positive integers seperated by spaces, denoting the list of numbers. The numbers are in ascending order and every number in this list is less than 10^{9}.

## Output

For each test case, output the number of numbers in this list which can be represented as an average of any two other numbers in the same list.

## Sample

3 1 2 3 6 3 4 6 7 8 9

1 3

## Hint

In the first case, 2 can be represented by (1 + 3) / 2.

In the second case, 6 can be represented by (3 + 9) / 2, 7 can be represented by (6 + 8) / 2, 8 can be represented by (7 + 9) / 2.

## Author

Staginner