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.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.*;

public class ArmChairs {
    static final Random random = new Random();

    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

        int[] readArray(int n, int size) {
            int[] a = new int[size];
            for (int i = 0; i < n; i++) {
                a[i] = this.nextInt();
            }

            return a;
        }

        long[] readLongArray(int n, int size) {
            long[] a = new long[size];
            for (int i = 0; i < n; i++) {
                a[i] = this.nextLong();
            }
            return a;
        }
    }

    static void ruffleSort(long[] a) {
        int n = a.length;//shuffle, then sort
        for (int i = 0; i < n; i++) {
            int oi = random.nextInt(n);
            long temp = a[oi];
            a[oi] = a[i];
            a[i] = temp;
        }
        Arrays.sort(a);
    }

    static void ruffleSort(int[] a) {
        int n = a.length;//shuffle, then sort
        for (int i = 0; i < n; i++) {
            int oi = random.nextInt(n), temp = a[oi];
            a[oi] = a[i];
            a[i] = temp;
        }
        Arrays.sort(a);
    }

    public static void main(String[] args) {
        FastReader fs = new FastReader();
        int t = 1;

        for (int z = 0; z < t; z++) {
            int n = fs.nextInt();
            List<Integer> empty = new ArrayList<>();
            List<Integer> chairs = new ArrayList<>();
            for(int i = 0; i < n; i++) {
                int status = fs.nextInt();
                if(status == 1) chairs.add(i+1);
                else empty.add(i+1);
            }
            int[][] dp = new int[empty.size() + 1][chairs.size() + 1];
            dp[0][0] = 0;
            for(int i = 1; i <= chairs.size(); i++) dp[0][i] = (int)3e+8;
            for(int i = 1; i <= empty.size(); i++) {
                for(int j = 1; j <= chairs.size(); j++) {
                    // Shift jth person to ith chair
                    dp[i][j] = dp[i-1][j-1] + Math.abs(empty.get(i-1) - chairs.get(j-1));
                    dp[i][j] = Math.min(dp[i][j], dp[i-1][j]);
                }
                //System.out.println(i + " " + Arrays.toString(dp[i]));
            }
            //System.out.println(empty.size() + " " + chairs.size());
            System.out.println(dp[empty.size()][chairs.size()]);
        }
    }
}