04. Personal Titles

using System;

namespace PersonalTitles
{
    class Program
    {
        static void Main(string[] args)
        {
            double age = double.Parse(Console.ReadLine());
            string gender = Console.ReadLine();

            if (age < 16 && gender == "m")
            {
                Console.WriteLine("Master");
            }
            else if (age >=16 && gender == "m")
            {
                Console.WriteLine("Mr.");
            }
            else if (gender == "f" && age < 16)
            {
                Console.WriteLine("Miss");
            }
            else if (gender == "f" && age >= 16)
            {
                Console.WriteLine("Ms.");
            }
        }
    }
}

Или така:

using System;

namespace PersonalTitles
{
    class Program
    {
        static void Main(string[] args)
        {
            double age = double.Parse(Console.ReadLine());
            string gender = Console.ReadLine();

            if (age < 16)
            {
                if (gender == "m")
                {
                    Console.WriteLine("Master");
                }
                else if (gender == "f")
                {
                    Console.WriteLine("Miss");
                }
            }
            else
            {
                if (gender == "m")
                {
                    Console.WriteLine("Mr.");
                }
                else if (gender == "f")
                {
                    Console.WriteLine("Ms.");
                }
            }
        }
    }
}

Тарикатско с тернарен оператор:

using System;

namespace PersonalTitles
{
    class Program
    {
        static void Main(string[] args)
        {
            double age = double.Parse(Console.ReadLine());
            string gender = Console.ReadLine();

            Console.WriteLine(age < 16 ? (gender == "m" ? "Master" : "Miss") : (gender == "m" ? "Mr." : "Ms."));
        }
    }
}