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.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.InputMismatchException;
import java.util.List;
import java.util.StringJoiner;

public class D {

  private static List<Long> chairs;
  private static List<Long> folks;
  private static Long[] data;
  private static Long[][] cache;

  public static void main(String[] args) {
    Print print = new Print();
    Scan scan = new Scan();

    int n = scan.scanInt();
    data = scan.scan1dLongArray();
    chairs = new ArrayList<>();
    folks = new ArrayList<>();
    cache = new Long[n][n];

    for (int i = 0; i < n; i++) {
      if (data[i] == 0) {
        chairs.add((long) i);
      } else {
        folks.add((long) i);
      }
    }

    print.printLine(Long.toString(solve(folks, chairs, 0, 0)));
    print.close();
  }

  private static long solve(List<Long> folks, List<Long> chairs, int i, int j) {
    if (i == folks.size()) {
      return 0;
    }
    if (j == chairs.size()) {
      return Integer.MAX_VALUE;
    }

    if (cache[i][j] != null) {
      return cache[i][j];
    }

    return cache[i][j] = Math
        .min(Math.abs(folks.get(i) - chairs.get(j)) + solve(folks, chairs, i + 1, j + 1),
            solve(folks, chairs, i, j + 1));

  }


  static class Scan {

    private byte[] buf = new byte[1024];
    private int index;
    private InputStream in;
    private int total;

    public Scan() {
      in = System.in;
    }

    public int scan() {
      if (total < 0) {
        throw new InputMismatchException();
      }
      if (index >= total) {
        index = 0;
        try {
          total = in.read(buf);
        } catch (IOException ignored) {
        }
        if (total <= 0) {
          return -1;
        }
      }
      return buf[index++];
    }

    public int scanInt() {
      int integer = 0;
      int n = scan();
      while (isWhiteSpace(n)) {
        n = scan();
      }
      int neg = 1;
      if (n == '-') {
        neg = -1;
        n = scan();
      }
      while (!isWhiteSpace(n)) {
        if (n >= '0' && n <= '9') {
          integer *= 10;
          integer += n - '0';
          n = scan();
        } else {
          throw new InputMismatchException();
        }
      }
      return neg * integer;
    }

    public double scanDouble() {
      double doub = 0;
      int n = scan();
      while (isWhiteSpace(n)) {
        n = scan();
      }
      int neg = 1;
      if (n == '-') {
        neg = -1;
        n = scan();
      }
      while (!isWhiteSpace(n) && n != '.') {
        if (n >= '0' && n <= '9') {
          doub *= 10;
          doub += n - '0';
          n = scan();
        } else {
          throw new InputMismatchException();
        }
      }
      if (n == '.') {
        n = scan();
        double temp = 1;
        while (!isWhiteSpace(n)) {
          if (n >= '0' && n <= '9') {
            temp /= 10;
            doub += (n - '0') * temp;
            n = scan();
          } else {
            throw new InputMismatchException();
          }
        }
      }
      return doub * neg;
    }

    public Integer[] scan1dIntArray() {
      String[] s = this.scanString().split(" ");
      Integer[] arr = new Integer[s.length];
      for (int i = 0; i < s.length; i++) {
        arr[i] = Integer.parseInt(s[i]);
      }
      return arr;
    }

    public Integer[][] scan2dIntArray(int n, int m) {
      Integer[][] arr = new Integer[n][m];
      for (int i = 0; i < n; i++) {
        String[] s = this.scanString().split(" ");
        for (int j = 0; j < m; j++) {
          arr[i][j] = Integer.parseInt(s[j]);
        }
      }
      return arr;
    }

    public String[] scan1dStringArray() {
      return this.scanString().split(" ");
    }

    public String[][] scan2dStringArray(int n, int m) {
      String[][] arr = new String[n][m];
      for (int i = 0; i < n; i++) {
        String[] s = this.scanString().split(" ");
        for (int j = 0; j < m; j++) {
          arr[i][j] = s[j];
        }
      }
      return arr;
    }

    public char[] scan1dCharArray() {
      return this.scanString().toCharArray();
    }

    public char[][] scan2dCharArray(int n, int m) {
      char[][] arr = new char[n][m];
      for (int i = 0; i < n; i++) {
        char[] s = this.scanString().toCharArray();
        for (int j = 0; j < m; j++) {
          arr[i][j] = s[j];
        }
      }
      return arr;
    }

    public Long[] scan1dLongArray() {
      String[] s = this.scanString().split(" ");
      Long[] arr = new Long[s.length];
      for (int i = 0; i < s.length; i++) {
        arr[i] = Long.parseLong(s[i]);
      }
      return arr;
    }

    public Long[][] scan2dLongArray(int n, int m) {
      Long[][] arr = new Long[n][m];
      for (int i = 0; i < n; i++) {
        String[] s = this.scanString().split(" ");
        for (int j = 0; j < m; j++) {
          arr[i][j] = Long.parseLong(s[j]);
        }
      }
      return arr;
    }

    public String scanString() {
      StringBuilder sb = new StringBuilder();
      int n = scan();
      while (isWhiteSpace(n)) {
        n = scan();
      }
      while (!isWhiteSpace(n)) {
        sb.append((char) n);
        n = scan();
      }
      return sb.toString();
    }

    private boolean isWhiteSpace(int n) {
      if (n == '\n' || n == '\r' || n == '\t' || n == -1) {
        return true;
      }
      return false;
    }
  }

  static class Print {

    private final BufferedWriter bw;

    public Print() {
      bw = new BufferedWriter(new OutputStreamWriter(System.out));
    }

    public void print(String str) {
      try {
        bw.append(str);
      } catch (IOException ignored) {
      }
    }

    public void printLine(Integer[] arr) {
      StringJoiner sj = new StringJoiner(" ");
      for (Integer x : arr) {
        sj.add(Integer.toString(x));
      }
      printLine(sj.toString());
    }

    public void printLine(Integer[][] arr) {
      for (Integer[] x : arr) {
        StringJoiner sj = new StringJoiner(" ");
        for (Integer y : x) {
          sj.add(Integer.toString(y));
        }
        printLine(sj.toString());
      }
    }

    public void printLine(String[] arr) {
      StringJoiner sj = new StringJoiner(" ");
      for (String x : arr) {
        sj.add(x);
      }
      printLine(sj.toString());
    }

    public void printLine(String[][] arr) {
      for (String[] x : arr) {
        StringJoiner sj = new StringJoiner(" ");
        for (String y : x) {
          sj.add(y);
        }
        printLine(sj.toString());
      }
    }

    public void printLine(char[] arr) {
      StringJoiner sj = new StringJoiner(" ");
      for (char x : arr) {
        sj.add(Character.toString(x));
      }
      printLine(sj.toString());
    }

    public void printLine(char[][] arr) {
      for (char[] x : arr) {
        StringJoiner sj = new StringJoiner(" ");
        for (char y : x) {
          sj.add(Character.toString(y));
        }
        printLine(sj.toString());
      }
    }

    public void printLine(Long[] arr) {
      StringJoiner sj = new StringJoiner(" ");
      for (Long x : arr) {
        sj.add(Long.toString(x));
      }
      printLine(sj.toString());
    }

    public void printLine(Long[][] arr) {
      for (Long[] x : arr) {
        StringJoiner sj = new StringJoiner(" ");
        for (Long y : x) {
          sj.add(Long.toString(y));
        }
        printLine(sj.toString());
      }
    }

    public void printLine(String str) {
      print(str);
      try {
        bw.append("\n");
      } catch (IOException ignored) {
      }
    }

    public void close() {
      try {
        bw.close();
      } catch (IOException ignored) {
      }
    }
  }

}
