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.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;

public class D {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        int t = 1;
        for (int i = 0; i < t; i++) {
            solve(sc, pw);
        }
        pw.close();
    }
    static void solve(Scanner in, PrintWriter out){
        int n = in.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = in.nextInt();
        }
        int[] pre = new int[n + 1];
        List<Integer> z = new ArrayList<>();
        List<Integer> o = new ArrayList<>();
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            if (arr[i] == 0) {
                cnt++;
                z.add(i);
            }else{
                o.add(i);
            }
        }
        int[][] dp = new int[cnt + 1][(n - cnt) + 1];
        int one = n - cnt;
        Arrays.fill(dp[0], 1000000);
        dp[0][0] = 0;
        int min = 10000000;
        for (int i = 1; i <= cnt; i++) {// the position of zero,
            Arrays.fill(dp[i], 1000000);
            for (int j = 1; j <= Math.min(one, i); j++) {// the position of one
                if (cnt - i < one - j){
                    dp[i][j] = 10000000;
                }else{
                    dp[i][j] = Math.min(dp[i - 1][j - 1] + Math.abs(o.get(j - 1) - z.get(i - 1)), dp[i - 1][j]);
                }
                if (j == one){
                    min = Math.min(min, dp[i][j]);
                }
            }
        }
        min = Math.min(min, dp[0][n - cnt]);
        out.println(min);
    }



    static boolean isPrime(long n)
    {
        // Corner cases
        if (n <= 1)
            return false;
        if (n <= 3)
            return true;

        // This is checked so that we can skip
        // middle five numbers in below loop
        if (n % 2 == 0 || n % 3 == 0)
            return false;

        for (int i = 5; i * i <= n; i = i + 6)
            if (n % i == 0 || n % (i + 2) == 0)
                return false;

        return true;
    }

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

    // method to return LCM of two numbers
    static long lcm(long a, long b)
    {
        return (a / gcd(a, b)) * b;
    }

    public static int[] sieveEratosthenes(int n) {
        if (n <= 32) {
            int[] primes = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31};
            for (int i = 0; i < primes.length; i++) {
                if (n < primes[i]) {
                    return Arrays.copyOf(primes, i);
                }
            }
            return primes;
        }

        int u = n + 32;
        double lu = Math.log(u);
        int[] ret = new int[(int) (u / lu + u / lu / lu * 1.5)];
        ret[0] = 2;
        int pos = 1;

        int[] isnp = new int[(n + 1) / 32 / 2 + 1];
        int sup = (n + 1) / 32 / 2 + 1;

        int[] tprimes = {3, 5, 7, 11, 13, 17, 19, 23, 29, 31};
        for (int tp : tprimes) {
            ret[pos++] = tp;
            int[] ptn = new int[tp];
            for (int i = (tp - 3) / 2; i < tp << 5; i += tp) ptn[i >> 5] |= 1 << (i & 31);
            for (int j = 0; j < sup; j += tp) {
                for (int i = 0; i < tp && i + j < sup; i++) {
                    isnp[j + i] |= ptn[i];
                }
            }
        }

        // 3,5,7
        // 2x+3=n
        int[] magic = {0, 1, 23, 2, 29, 24, 19, 3, 30, 27, 25, 11, 20, 8, 4, 13, 31, 22, 28, 18, 26, 10, 7, 12, 21, 17, 9, 6, 16, 5, 15, 14};
        int h = n / 2;
        for (int i = 0; i < sup; i++) {
            for (int j = ~isnp[i]; j != 0; j &= j - 1) {
                int pp = i << 5 | magic[(j & -j) * 0x076be629 >>> 27];
                int p = 2 * pp + 3;
                if (p > n) break;
                ret[pos++] = p;
                if ((long) p * p > n) continue;
                for (int q = (p * p - 3) / 2; q <= h; q += p) isnp[q >> 5] |= 1 << q;
            }
        }

        return Arrays.copyOf(ret, pos);
    }

    //    reverse division for 2
    public static long[] rdiv2(int n, int mod){
        long[] arr = new long[n + 5];
        arr[0] = 1;
        long rev2 = (mod + 1) / 2;
        for (int i = 1; i < n; i++) {
            arr[i] = arr[i - 1] * rev2 % mod;
        }
        return arr;
    }
    static List<Integer> primeFactors(int n)
    {
        // Print the number of 2s that divide n
        List<Integer> ls = new ArrayList<>();
        if (n % 2 == 0) ls.add(2);
        while (n%2==0)
        {
            n /= 2;
        }

        // n must be odd at this point.  So we can
        // skip one element (Note i = i +2)
        for (int i = 3; i <= Math.sqrt(n); i+= 2)
        {
            // While i divides n, print i and divide n
            if (n  % i == 0) ls.add(i);
            while (n%i == 0)
            {
                n /= i;
            }
        }
        if (n > 1) ls.add(n);
        return ls;
    }

    static int find(int i, int[] par){
        if (par[i] < 0) return i;
        return par[i] = find(par[i], par);
    }
    static boolean union(int i, int j, int[] par){
        int pi = find(i, par);
        int pj = find(j, par);
        if (pi == pj) return false;
        if (par[pi] < par[pj]){
            par[pi] += par[pj];
            par[pj] = pi;
        }else{
            par[pj] += par[pi];
            par[pi] = pj;
        }
        return true;
    }
}
