//Rextester.Program.Main is the entry point for your code. Don't change it.

//Microsoft (R) Visual C# Compiler version 2.9.0.63208 (958f2354)

​

using System;

​

namespace Rextester

{

    public class Program

    {

        public static void Main(string[] args)

        {

            Console.WriteLine("あなたの年齢を入力してください：");

            int age = int.Parse(Console.ReadLine());

            bool adulthood = age >= 20;

            string msg = "成年者です。";

            if (adulthood == false){

                msg = "未" + msg;

            }

            Console.WriteLine(msg);

​

        }

    }

}