import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        TreeSet<Integer> evStops = new TreeSet<>();
        TreeSet<Integer> oddStops = new TreeSet<>();
        for (int i = 0; i < n; i++) {
            if (sc.nextInt() == 1) {
                if (i % 2 == 0) {
                    oddStops.add(i);
                } else {
                    evStops.add(i);
                }
            } else {
                if (i % 2 == 0) {
                    evStops.add(i);
                } else {
                    oddStops.add(i);
                }
            }
        }
        evStops.add(n - 1);
        oddStops.add(n - 1);
        long ans = 0;
        for (int i = 0; i < n - 1; i++) {
            if (i % 2 == 0) {
                ans += evStops.first() - i;
            } else {
                ans += oddStops.first() - i;
            }
            evStops.remove(i);
            oddStops.remove(i);
        }
        System.out.println(ans);
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}