using System;

public class Program
{
	public static void Main()
	{
		Console.Write("Enter a natural number: ");
		int n = int.Parse(Console.ReadLine());
		int broika = 0;

		if (n > 0 && n % 1 == 0)
		{
			for (int i = 0; i <= n; i++)
			{
				Console.Write("Enter a 4-digit natural number: ");
				int num = int.Parse(Console.ReadLine());
				if (num >= 1000 && num <= 9999)
				{
					if (num / 100 % 10 == 0) {
						broika++;
					}
				} else {
					Console.WriteLine("The number that you have entered is not a 4-digit natural number");
					break;
				}
			}
			Console.WriteLine(broika);
	} else
	Console.WriteLine( "The number that you have entered is not natural." ) ; } }