write a go solution for Description:
There are n armchairs, numbered from 1 to n from left to right. Some armchairs are occupied by people (at most one person per armchair), others are not. The number of occupied armchairs is not greater than n/2.

For some reason, you would like to tell people to move from their armchairs to some other ones. If the i-th armchair is occupied by someone and the j-th armchair is not, you can tell the person sitting in the i-th armchair to move to the j-th armchair. The time it takes a person to move from the i-th armchair to the j-th one is |i-j| minutes. You may perform this operation any number of times, but these operations must be done sequentially, i. e. you cannot tell a person to move until the person you asked to move in the last operation has finished moving to their destination armchair.

You want to achieve the following situation: every seat that was initially occupied must be free. What is the minimum time you need to do it?

Input Format:
The first line contains one integer n (2<=n<=5000) — the number of armchairs.

The second line contains n integers a_1,a_2,...,a_n (0<=a_i<=1). a_i=1 means that the i-th armchair is initially occupied, a_i=0 means that it is initially free. The number of occupied armchairs is at most n/2.

Output Format:
Print one integer — the minimum number of minutes you have to spend to achieve the following situation: every seat that was initially occupied must be free.

Note:
In the first test, you can perform the following sequence:

1. ask a person to move from armchair 1 to armchair 2, it takes 1 minute;
2. ask a person to move from armchair 7 to armchair 6, it takes 1 minute;
3. ask a person to move from armchair 4 to armchair 5, it takes 1 minute.

In the second test, you can perform the following sequence:

1. ask a person to move from armchair 1 to armchair 4, it takes 3 minutes;
2. ask a person to move from armchair 2 to armchair 6, it takes 4 minutes;
3. ask a person to move from armchair 4 to armchair 5, it takes 1 minute;
4. ask a person to move from armchair 3 to armchair 4, it takes 1 minute.

In the third test, no seat is occupied so your goal is achieved instantly.. Output only the code with no comments, explanation, or additional text.