Armchairs

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

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

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.

Examples

Input

7 1 0 0 1 0 0 1

Output

3

Input

6 1 1 1 0 0 0

Output

9

Input

5 0 0 0 0 0

Output

0

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.

inputFormat

Input

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.

outputFormat

Output

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.

Examples

Input

7 1 0 0 1 0 0 1

Output

3

Input

6 1 1 1 0 0 0

Output

9

Input

5 0 0 0 0 0

Output

0

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.

样例

6
1 1 1 0 0 0

9

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