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.util.*;import java.io.*;import java.math.*;
public class CF1525D
{
    static final Random random=new Random();
    static boolean memory = true;
    
    static void ruffleSort(int[] a) {
        int n = a.length; 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n), temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        ArrayList<Integer> lst = new ArrayList<>();
        for(int i : a)
            lst.add(i);
        Collections.sort(lst);
        for(int i = 0; i < n; i++)
            a[i] = lst.get(i);
    }

    static void ruffleSort(long[] a) {
        int n = a.length; 
        for (int i=0; i<n; i++) {
            int oi=random.nextInt(n);
            long temp=a[oi];
            a[oi]=a[i]; a[i]=temp;
        }
        ArrayList<Long> lst = new ArrayList<>();
        for(long i : a)
            lst.add(i);
        Collections.sort(lst);
        for(int i = 0; i < n; i++)
            a[i] = lst.get(i);
    }

    static int[][] dp;
    static ArrayList<Integer> zero, one;

    static int solve(int p1, int p0){
        if(p1 == one.size())
            return 0;
        if(one.size() - p1 > zero.size() - p0)
            return Integer.MAX_VALUE;
        if(dp[p1][p0] != -1)
            return dp[p1][p0];
        return dp[p1][p0] = Math.min(solve(p1, p0+1), Math.abs(zero.get(p0)-one.get(p1)) + solve(p1+1, p0+1));
    }

    public static void process()throws IOException
    {
        int n = ni();
        int[] a = nai(n);
        zero = new ArrayList<>();
        one = new ArrayList<>();
        int c = 0;
        for(int i : a){
            if(i == 0)
                zero.add(c);
            else
                one.add(c);
            c++;
        }
        int p = one.size(), q = zero.size();
        dp = new int[p][q];
        for(int i = 0; i < p; i++)
            for(int j = 0; j < q; j++)
                dp[i][j] = -1;
        int ans = solve(0, 0);
        pn(ans);
    }
   
    static AnotherReader sc;
    static PrintWriter out;

    public static void main(String[] args) throws Exception{
        if(memory)new Thread(null, new Runnable() {public void run(){try{new CF1525D().run();}catch(Exception e){e.printStackTrace();System.exit(1);}}}, "1", 1 << 28).start();
        else new CF1525D().run();
    }

    void run()throws Exception
    {
        boolean oj = System.getProperty("ONLINE_JUDGE") != null;
        if(oj){sc=new AnotherReader();out=new PrintWriter(System.out);}
        else{sc=new AnotherReader(100);out=new PrintWriter("output.txt");}
        long s = System.currentTimeMillis();
        int t=1;
        //t=ni();
        //int k = t;
        while(t-->0) {/*p("Case #"+ (k-t) + ": ")*/;process();}
        out.flush();
        System.err.println(System.currentTimeMillis()-s+"ms");
        out.close();
    }

    static long power(long k, long c, long mod){
        long y = 1;
        while(c > 0){
            if(c%2 == 1)
                y = y * k % mod;
            c = c/2;
            k = k * k % mod;
        }
        return y;
    }

    static int power(int x, int y, int p){ 
        int res = 1;
        x = x % p;
        while (y > 0) {
            if (y % 2 == 1)
                res = (res * x) % p;
            y = y >> 1;
            x = (x * x) % p;
        }
        return res;
    }

    static int log2(int N)
    {
        int result = (int)(Math.log(N) / Math.log(2));
        return result;
    }

 
    static void pn(Object o){out.println(o);}
    static void pn(int[] a){for(int i : a)out.print(i+" ");pn("");}
    static void pn(long[] a){for(long i : a)out.print(i+" ");pn("");}
    static void p(Object o){out.print(o);}
    static void YES(){out.println("YES");}
    static void NO(){out.println("NO");}
    static void yes(){out.println("yes");}
    static void no(){out.println("no");}
    static void p(int[] a){for(int i : a)out.print(i+" ");}
    static void p(long[] a){for(long i : a)out.print(i+" ");}
    static void pni(Object o){out.println(o);out.flush();}
    static int ni()throws IOException{return sc.nextInt();}
    static long nl()throws IOException{return sc.nextLong();}
    static double nd()throws IOException{return sc.nextDouble();}
    static String nln()throws IOException{return sc.nextLine();}
    static String ns()throws IOException{return sc.next();}
    static int[] nai(int N)throws IOException{int[]A=new int[N];for(int i=0;i!=N;i++){A[i]=ni();}return A;}
    static long[] nal(int N)throws IOException{long[]A=new long[N];for(int i=0;i!=N;i++){A[i]=nl();}return A;}
    static long gcd(long a, long b)throws IOException{return (b==0)?a:gcd(b,a%b);}
    static int gcd(int a, int b)throws IOException{return (b==0)?a:gcd(b,a%b);}
    static int bit(long n)throws IOException{return (n==0)?0:(1+bit(n&(n-1)));}
    
/////////////////////////////////////////////////////////////////////////////////////////////////////////
 
    static class AnotherReader{BufferedReader br; StringTokenizer st;
    AnotherReader()throws FileNotFoundException{
    br=new BufferedReader(new InputStreamReader(System.in));}
    AnotherReader(int a)throws FileNotFoundException{
    br = new BufferedReader(new FileReader("input.txt"));}
    String next()throws IOException{
    while (st == null || !st.hasMoreElements()) {try{
    st = new StringTokenizer(br.readLine());}
    catch (IOException  e){ e.printStackTrace(); }}
    return st.nextToken(); } int nextInt() throws IOException{
    return Integer.parseInt(next());}
    long nextLong() throws IOException
    {return Long.parseLong(next());}
    double nextDouble()throws IOException { return Double.parseDouble(next()); }
    String nextLine() throws IOException{ String str = ""; try{
    str = br.readLine();} catch (IOException e){
    e.printStackTrace();} return str;}}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////
}