using System;

public class Program

{

    public static void Main()

    {

        char[] array = { 'G', 'A', 'T' };

        switch (array [0])

        {

            case 'G':

                Console.WriteLine('G');

            switch (array [1])

                    {

                        case 'A':

                        Console.WriteLine('A');

                        switch (array [2])

                        {

                            case 'T':

                            Console.WriteLine('T');

                            Console.WriteLine("Protein sequence is found");

                            break;

                        }

                break;

            }

            break;

        }

    }

}