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.*;

public class a2oj implements Runnable {

    static FastReader sc;
    static PrintWriter out;
    static int mod = 1000000007;

    public static void main(String[] args) {
        new Thread(null, new a2oj(), "coderrohan14", 1 << 26).start();
    }

    @Override
    public void run() {
        try {
            ioSetup();
        } catch (IOException e) {
            return;
        }
    }

    public static void ioSetup() throws IOException {
        if (System.getProperty("ONLINE_JUDGE") == null) {
            File f1 = new File("input.txt");
            File f2 = new File("output.txt");
            Reader r = new FileReader(f1);
            sc = new FastReader(r);
            out = new PrintWriter(f2);
            double prev = System.currentTimeMillis();
            solve();
            out.println("\n\nExecuted in : " + ((System.currentTimeMillis() - prev) / 1e3) + " sec");
        } else {
            sc = new FastReader(new InputStreamReader(System.in));
            out = new PrintWriter(System.out);
            solve();
        }
        out.flush();
        out.close();
    }

    static int n, arr[], dp[][];
    static ArrayList<Integer> ones, zeroes;

    static void solve() {
        // int t = sc.nextInt();
        // StringBuilder ans = new StringBuilder("");
        // while (t-- > 0) {

        // }
        // out.println(ans);
        n = sc.nextInt();
        ones = new ArrayList<>();
        zeroes = new ArrayList<>();
        arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
            if (arr[i] == 1) {
                ones.add(i);
            } else {
                zeroes.add(i);
            }
        }
        dp = new int[zeroes.size() + 1][ones.size() + 1];
        for (int i = 0; i <= zeroes.size(); i++) {
            Arrays.fill(dp[i], -1);
        }
        out.println(armch(0, 0, zeroes.size(), ones.size()));
    }

    static int armch(int i, int j, int n, int m) {
        if (j == m)
            return 0;
        int zs = n - i, os = m - j;
        if (zs < os)
            return Integer.MAX_VALUE;
        if (dp[i][j] != -1)
            return dp[i][j];
        int a1 = armch(i + 1, j, n, m);
        int a2 = armch(i + 1, j + 1, n, m);
        if (a2 != Integer.MAX_VALUE)
            a2 += Math.abs(zeroes.get(i) - ones.get(j));
        int min = Math.min(a1, a2);
        return dp[i][j] = min;
    }

    /****************************************************************************************************************************************************************************************/

    static long modInverse(long a, int mod) {
        long g = gcd(a, mod);
        if (g != 1)
            return -1;
        else {
            return modPower(a, mod - 2L, mod);
        }
    }

    static long modPower(long x, long y, int mod) {
        long res = 1;
        x = x % mod;
        if (x == 0)
            return 0;
        while (y > 0) {
            if ((y & 1) != 0)
                res = (res * x) % mod;
            y = y >> 1;
            x = (x * x) % mod;
        }
        return res;
    }

    static int gcd(int a, int b) {
        int tmp = 0;
        while (b != 0) {
            tmp = b;
            b = a % b;
            a = tmp;
        }
        return a;
    }

    static long gcd(long a, long b) {
        long tmp = 0;
        while (b != 0) {
            tmp = b;
            b = a % b;
            a = tmp;
        }
        return a;
    }

    static boolean isPrime(long n) {
        if (n == 2 || n == 3)
            return true;
        if (n % 2 == 0)
            return false;
        for (long i = 3; i * i <= n; i += 2) {
            if (n % i == 0)
                return false;
        }
        return n != 1;
    }

    static boolean isPerfectSquare(long x) {
        long sqrt = (long) Math.sqrt(x);
        return (sqrt * sqrt) == x;
    }

    static int digitsCount(long x) {
        return (int) Math.floor(Math.log10(x)) + 1;
    }

    static boolean isPowerTwo(long n) {
        return (n & n - 1) == 0;
    }

    static void sieve(boolean[] prime, int n) { // Sieve Of Eratosthenes
        for (int i = 1; i <= n; i++) {
            prime[i] = true;
        }
        for (int i = 2; i * i <= n; i++) {
            if (prime[i]) {
                for (int j = 2; i * j <= n; j++) {
                    prime[i * j] = false;
                }
            }
        }
    }

    static long nCr(long n, long r) { // Combinations
        if (n < r)
            return 0;
        if (r > n - r) { // because nCr(n, r) == nCr(n, n - r)
            r = n - r;
        }
        long ans = 1L;
        for (long i = 0; i < r; i++) {
            ans *= (n - i);
            ans /= (i + 1);
        }
        return ans;
    }

    static int floor(int[] a, int v) {
        int l = 0, h = a.length - 1;
        while (l < h) {
            int mid = (l + h) / 2;
            if (a[mid] == v)
                return mid;
            if (v < a[mid])
                h = mid;
            else {
                if (mid + 1 < h && a[mid + 1] < v)
                    l = mid + 1;
                else
                    return mid;
            }
        }
        return a[l] <= v ? l : -1;
    }

    static int floor(long[] a, long v) {
        int l = 0, h = a.length - 1;
        while (l < h) {
            int mid = (l + h) / 2;
            if (a[mid] == v)
                return mid;
            if (v < a[mid])
                h = mid;
            else {
                if (mid + 1 < h && a[mid + 1] < v)
                    l = mid + 1;
                else
                    return mid;
            }
        }
        return a[l] <= v ? l : -1;
    }

    static int ceil(int[] a, int v) {
        int l = 0, h = a.length - 1;
        while (l < h) {
            int mid = (l + h) / 2;
            if (a[mid] == v)
                return mid;
            if (a[mid] < v)
                l = mid + 1;
            else
                h = mid;
        }
        return a[h] >= v ? h : -1;
    }

    static int ceil(long[] a, long v) {
        int l = 0, h = a.length - 1;
        while (l < h) {
            int mid = (l + h) / 2;
            if (a[mid] == v)
                return mid;
            if (a[mid] < v)
                l = mid + 1;
            else
                h = mid;
        }
        return a[h] >= v ? h : -1;
    }

    static long catalan(int n) { // n-th Catalan Number
        long c = nCr(2 * n, n);
        return c / (n + 1);
    }

    static class Pair implements Comparable<Pair> { // Pair Class
        int x;
        int y;

        public Pair(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof Pair)) {
                return false;
            }

            Pair pair = (Pair) o;

            if (x != pair.x) {
                return false;
            }
            if (y != pair.y) {
                return false;
            }

            return true;
        }

        @Override
        public int hashCode() {
            long result = x;
            result = 31 * result + y;
            return (int) result;
        }

        @Override
        public int compareTo(Pair o) {
            return (int) (this.x - o.x);
        }
    }

    static class Trip { // Triplet Class
        long x;
        long y;
        long z;

        Trip(long x, long y, long z) {
            this.x = x;
            this.y = y;
            this.z = z;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (!(o instanceof Trip)) {
                return false;
            }

            Trip trip = (Trip) o;

            if (x != trip.x) {
                return false;
            }
            if (y != trip.y) {
                return false;
            }
            if (z != trip.z) {
                return false;
            }
            return true;
        }

        @Override
        public int hashCode() {
            long result = 62 * x + 31 * y + z;
            return (int) result;
        }
    }

    /**************************************************************************************************************************************************************************************/

    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader(Reader r) {
            br = new BufferedReader(r);
        }

        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());
        }

        int[] readArrayI(int n) {
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = sc.nextInt();
            }
            return arr;
        }

        long[] readArrayL(int n) {
            long[] arr = new long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = sc.nextLong();
            }
            return arr;
        }

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

    /*
     * ASCII Range--->(A-Z)--->[65,90]<<::>>(a-z)--->[97,122]
     */
    /******************************************************************************************************************/

    static void printArray(int[] arr) {
        out.print("[");
        for (int i = 0; i < arr.length; i++) {
            if (i < arr.length - 1)
                out.print(arr[i] + ",");
            else
                out.print(arr[i]);
        }
        out.print("]");
        out.println();
    }

    static void printArray(long[] arr) {
        out.print("[");
        for (int i = 0; i < arr.length; i++) {
            if (i < arr.length - 1)
                out.print(arr[i] + ",");
            else
                out.print(arr[i]);
        }
        out.print("]");
        out.println();
    }

    static void printArray(double[] arr) {
        out.print("[");
        for (int i = 0; i < arr.length; i++) {
            if (i < arr.length - 1)
                out.print(arr[i] + ",");
            else
                out.print(arr[i]);
        }
        out.print("]");
        out.println();
    }
    /**********************************************************************************************************************/
}