using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { string[] ncen = new string[11]; for (int i = 0; i < 9; i++) { ncen[i] = args[i]; } for(int i = 0; i < 9;i++) { if((i+1) != int.Parse(ncen[i])) { Console.WriteLine(i+1); break; } } } } }