Number_0_to_100_to_Text_Dict

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Number_0_to_100_to_Text_Dict
{
    class Program
    {
        static void Main(string[] args)
        {
            var number = int.Parse(Console.ReadLine());
            if (number < 0)
            {
                Console.WriteLine("invalid number");
            }
            else
            {
                int unuts = number % 10;
                int tenths = number / 10;

                var num_to_text = new Dictionary<int, string>()
            {
                {0, "zero"      },
                {1, "one"       },
                {2, "two"       },
                {3, "three"     },
                {4, "four"      },
                {5, "five"      },
                {6, "six"       },
                {7, "seven"     },
                {8, "eight"     },
                {9, "nine"      },
                {10, "ten"      },
                {11, "eleven"   },
                {12, "twelve"   },
                {13, "thirteen" },
                {14, "fourteen" },
                {15, "fifteen"  },
                {16, "sixteen"  },
                {17, "seventeen"},
                {18, "eighteen" },
                {19, "nineteen" },
                {20, "twenty"   },
                {30, "thirty"   },
                {40, "fourty"   },
                {50, "fifty"    },
                {60, "sixty"    },
                {70, "seventy"  },
                {80, "eighty"   },
                {90, "ninety"   },
                {100, "hundred" }
            };
                if (number > 100)
                {
                    Console.WriteLine("invalid number");
                }
                else if (number == 100)
                {
                    Console.WriteLine("one " + num_to_text[number]);
                }
                else if (
                   (number >= 0 && number < 21) ||
                    number == 30 ||
                    number == 40 ||
                    number == 50 ||
                    number == 60 ||
                    number == 70 ||
                    number == 80 ||
                    number == 90)
                {
                    Console.WriteLine(num_to_text[number]);
                }
                else
                {
                    Console.WriteLine(num_to_text[(tenths * 10)] + " " + num_to_text[unuts]);
                }
            }



        }
    }
}