import java.util.*;

public class ex17 {
    public static void main(String []args)
    {
        Scanner in = new Scanner(System.in);
        int num = 0;
        int counter = 0;
        while(num != -1)
        {
            System.out.println("Enter number between 0-9 and enter -1 to finish");
            int newnum = in.nextInt();
            if(num == newnum-1)
            {
                counter++;
            }
            num = newnum;
        }
        System.out.println(counter);
    }
}