DOBRI

문제

You are given a sequence A consisting of N integers (not to be confused with the sequence from the previous task). We will call the i^th sequence element good if it equals the sum of some three elements in positions strictly smaller than i (an element can be used more than once in the sum). 

How many good elements does the sequence contain?

입력

The first line of input contains the positive integer N (1 ≤ N ≤ 5000), the length of the sequence A.

The second line of input contains N space-separated integers representing the sequence A (-100 000 ≤ A_i ≤ 100 000).

출력

The first and only line of output must contain the number of good elements in the sequence.

 

2
1 3

1

6
1 2 3 5 7 10

4

3
-1 2 0

1