Problem Statement

There is a sequence $A$ of positive integers consisting of $N$ terms, from the $0$-th term to the $N-1$-th term.
However, the values of some $0$ or more of the terms can be chosen freely.
Define a sequence $B$ of positive integers consisting of $N$ terms, from the $0$-th term to the $N-1$-th term, as follows.

$\displaystyle B_k = \sum_{i\& j=k} (A_i \times A_j)$

Input

$N$
$A_0\ A_1\ \ldots A_{N-1}$

$1 \leq N \leq 2 \times 10^5$
$1 \leq A_i \leq 10^9$ or $A_i=-1$
The value of the $i$-th term can be chosen freely among positive integers if and only if $A_i=-1$
All inputs are integers

Output

Output the answer in one line.

Sample

3
-1 -1 -1

-1

5
7 9 3 5 1

1

5
-1 54 -1 12 -1

36