题目描述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?

输入格式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 10⁹.

输出格式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.

样例Sample

提示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.