content: import java.io.*;
  import java.math.*;
  import java.security.*;
  import java.text.*;
  import java.util.*;
  import java.util.concurrent.*;
  import java.util.regex.*;
  
  public class Solution {
  
    // Complete the jumpingOnClouds function below.
    static int jumpingOnClouds(int[] c) {
      class Pair {
        int p; int c;
        Pair(int p, int c) { this.p = p; this.c = c; }
      }
      int minPath = Integer.MAX_VALUE;
      LinkedList<Pair> stack = new LinkedList<>();
      stack.push(new Pair(0, 0));
      while (stack.size() != 0) {
        Pair pos = stack.pop();
        if (pos.p + 1 < c.length && c[pos.p + 1] != 1) {
          stack.push(new Pair(pos.p + 1, pos.c + 1));
        }
        if (pos.p + 2 < c.length && c[pos.p + 2] != 1) {
          stack.push(new Pair(pos.p + 2, pos.c + 1));
        }
        if (pos.p + 1 >= c.length) {
          minPath = Math.min(minPath, pos.c);
        }
      }
      return minPath;
    }
  
    private static final Scanner scanner = new Scanner(System.in);
  
    public static void main(String[] args) throws IOException {
      BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
  
      int n = scanner.nextInt();
      scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
  
      int[] c = new int[n];
  
      String[] cItems = scanner.nextLine().split(" ");
      scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
  
      for (int i = 0; i < n; i++) {
        int cItem = Integer.parseInt(cItems[i]);
        c[i] = cItem;
      }
  
      int result = jumpingOnClouds(c);
  
      bufferedWriter.write(String.valueOf(result));
      bufferedWriter.newLine();
  
      bufferedWriter.close();
  
      scanner.close();
    }
  }
  