using System;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = Convert.ToInt32(Console.ReadLine());
            string [] ch= new string [100];
            string c;
            for (int i=0;i<n;i++)
                ch[i]=Console.ReadLine();
            c=Console.ReadLine();
            for (int i=0;i<n;i++)
            {
                if (c==ch[i].Substring(0,1)) Console.WriteLine(ch[i]);
            }
            Console.ReadKey();
        }
    }
}

what's the problem??? help me please

Use comment for this line (or delete this line)

            //Console.ReadKey();