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.*;
import java.util.ArrayList;
import java.util.StringTokenizer;

import static java.lang.Double.parseDouble;
import static java.lang.Integer.compare;
import static java.lang.Integer.parseInt;
import static java.lang.Long.parseLong;
import static java.lang.System.in;
import static java.lang.System.out;
import static java.util.Arrays.asList;
import static java.util.Collections.max;
import static java.util.Collections.min;

public class Main {
    private static final int MOD = (int) (1E9 + 7);
    private static final int INF = (int) (1E9);
    static FastScanner scanner = new FastScanner(in);

    public static void main(String[] args) throws IOException {
        // Write your solution here
        StringBuilder answer = new StringBuilder();
        int t = 1;
        // t = parseInt(scanner.nextLine());
        while (t-- > 0) {
            answer.append(solve()).append("\n");
        }
        out.println(answer);
    }

    private static Object solve() throws IOException {
        int n = scanner.nextInt();
        Integer[] a = new Integer[n];
        ArrayList<Integer> one = new ArrayList<>(), zero = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            a[i] = scanner.nextInt();
            if (a[i] == 0) zero.add(i);
            else one.add(i);
        }
        int[][] dp = new int[one.size() + 1][zero.size() + 1]; // minimum cost using i one and j zeros
        for (int i = 0; i <= one.size(); i++) {
            for (int j = 0; j <= zero.size(); j++) {
                dp[i][j] = INF;
            }
        }
        for (int i = 0; i <= zero.size(); i++) {
            dp[0][i] = 0;
        }
        for (int i = 1; i <= one.size(); i++) {
            for (int j = 1; j <= zero.size(); j++) {
                dp[i][j] = minn(dp[i - 1][j - 1] + Math.abs(one.get(i - 1) - zero.get(j - 1)), dp[i][j-1]);
            }
        }
        return dp[one.size()][zero.size()];
    }

    private static int maxx(Integer... a) {
        return max(asList(a));
    }

    private static int minn(Integer... a) {
        return min(asList(a));
    }

    private static long maxx(Long... a) {
        return max(asList(a));
    }

    private static long minn(Long... a) {
        return min(asList(a));
    }

    private static int add(int a, int b) {
        long res = ((long) (a + MOD) % MOD + (b + MOD) % MOD) % MOD;
        return (int) res;
    }

    private static int mul(int a, int b) {
        long res = ((long) a % MOD * b % MOD) % MOD;
        return (int) res;
    }

    private static int pow(int a, int b) {
        a %= MOD;
        int res = 1;
        while (b > 0) {
            if ((b & 1) != 0)
                res = mul(res, a);
            a = mul(a, a);
            b >>= 1;
        }
        return res;
    }

    private static int gcd(int a, int b) {
        if (b == 0)
            return a;
        return gcd(b, a % b);
    }

    private static int lcm(int a, int b) {
        return (a / gcd(a, b)) * b;
    }

    private static class Pair implements Comparable<Pair> {
        int index, value;

        public Pair(int index, int value) {
            this.index = index;
            this.value = value;
        }

        public int compareTo(Pair o) {
            if (value != o.value) return compare(value, o.value);
            return compare(index, o.index);
        }
    }

    static class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        FastScanner(File f) {
            try {
                br = new BufferedReader(new FileReader(f));
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }

        FastScanner(InputStream f) {
            br = new BufferedReader(new InputStreamReader(f));
        }

        String nextLine() {
            try {
                return br.readLine();
            } catch (IOException e) {
                return null;
            }
        }

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

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

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

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

    }
}