static void Main(string[] args) { Graph g = new Graph(); Console.WriteLine("===================================\n Manual Input, press key 0\n Input using File press key 1 \n\n If you press another keys, \n program is terminated .\n==================================="); switch (Console.ReadKey().KeyChar) { case '0': MInput(g); break; case '1': if (FInput(g) == false) { Console.ReadLine(); return; } break; default: return; } string input; do { Console.WriteLine("\n Please enter two cities where you want to find \n example) Seoul Busan \n===================================\n"); input = Console.ReadLine(); if (input != "0") { try { string[] tmp = input.Split(' '); int? t = g.Exec(tmp[0], tmp[1]); if (t == null) { Console.WriteLine("This input is invalid."); } else { Console.WriteLine("The time required " + (int)t + " hour(s)."); } }catch { Console.WriteLine(" This input is invalid.\n"); } } } while (input != "0"); Console.ReadLine(); }