public static void Main()
Console.WriteLine("A. B.");
Console.WriteLine("C. D.");
string ans1 = Console.ReadLine();
if (ans1 == "" || ans1 == "" || ans1 == "" || ans1 == "" || ans1 == "")
Console.WriteLine(" " );}
Console.WriteLine("A. B.");
Console.WriteLine("C. D.");
string ans2 = Console.ReadLine();
if (ans2 == "" || ans2 == "" || ans2 == "" || ans2 == "" || ans2 == "")
Console.WriteLine(" " );}