english-28 Sum Number

描述

Given a sequence of N number. How many numbers in the sequence are there which equal to the sum of two different numbers in the sequence.

输入

First line: one positive integers N (N <= 100).Second line: N positive integers (<= 100000).

输出

One integer.

样例输入

1
24
1 3 4 2

样例输出

12

限制

• 时间限制：1000ms
• 内存限制：128MB