write a go solution for Description:
Lee couldn't sleep lately, because he had nightmares. In one of his nightmares (which was about an unbalanced global round), he decided to fight back and propose a problem below (which you should solve) to balance the round, hopefully setting him free from the nightmares.

A non-empty array b_1,b_2,ldots,b_m is called good, if there exist m integer sequences which satisfy the following properties:

- The i-th sequence consists of b_i consecutive integers (for example if b_i=3 then the i-th sequence can be (-1,0,1) or (-5,-4,-3) but not (0,-1,1) or (1,2,3,4)).
- Assuming the sum of integers in the i-th sequence is sum_i, we want sum_1+sum_2+ldots+sum_m to be equal to 0.

You are given an array a_1,a_2,ldots,a_n. It has 2^n-1 nonempty subsequences. Find how many of them are good.

As this number can be very large, output it modulo 10^9+7.

An array c is a subsequence of an array d if c can be obtained from d by deletion of several (possibly, zero or all) elements.

Input Format:
The first line contains a single integer n (2<=n<=2*10^5) — the size of array a.

The second line contains n integers a_1,a_2,ldots,a_n (1<=a_i<=10^9) — elements of the array.

Output Format:
Print a single integer — the number of nonempty good subsequences of a, modulo 10^9+7.

Note:
For the first test, two examples of good subsequences are [2,7] and [2,2,4,7]:

For b=[2,7] we can use (-3,-4) as the first sequence and (-2,-1,ldots,4) as the second. Note that subsequence [2,7] appears twice in [2,2,4,7], so we have to count it twice.

Green circles denote (-3,-4) and orange squares denote (-2,-1,ldots,4).

For b=[2,2,4,7] the following sequences would satisfy the properties: (-1,0), (-3,-2), (0,1,2,3) and (-3,-2,ldots,3). Output only the code with no comments, explanation, or additional text.