using System;

namespace Test
{
	class Program
	{
		static void Main()
		{
			int[] a = { 5, 8, -3, 6, -4, 12, -19, 7, -2, 11, 5, -3, 15 };
			double sum = 0;

			for(int i = 0; i < a.Length; i++)
			{
				if(a[i] < 0)
				{
					sum += a[i];
				}
			}

			sum /= a.Length;

			Console.WriteLine("Arithmetic mean: " + sum);
			Console.ReadKey();
		}
	}
}