Problem Q
A+B Problem

Given $N$ integers in the range $[-50000,50000]$, how many ways are there to pick three integers $a_i$, $a_j$, $a_k$, such that $i$, $j$, $k$ are pairwise distinct and $a_i+a_j=a_k$? Two ways are different if their ordered triples $(i,j,k)$ of indices are different.

Input

The first line of input consists of a single integer $N$ ($1\le N\le 200000$). The next line consists of $N$ space-separated integers $a_1,a_2,\dots ,a_N$.

Output

Output an integer representing the number of ways.

4
1 2 3 4

4

6
1 1 3 3 4 6

10