using System;

    public class Program

    {

        public static void Main()

        {

            Phone phone1 = new Phone();

            phone1.SetPhone("1234567890", 100, 2);

            Console.WriteLine(phone1.GetPhoneDetails());

            phone1.Call(20);

            Console.WriteLine(phone1.GetPhoneDetails());

            Console.WriteLine("{0}", (phone1.SendSms()) ? "Send sms" : "sms failure");

            Console.WriteLine("{0}", (phone1.SendSms()) ? "Send sms" : "sms failure");

            Console.WriteLine("{0}", (phone1.SendSms()) ? "Send sms" : "sms failure");

        }

    }

    public class Phone

    {

        private string phoneNumber;

        private int airTime;

        private int sms;

            public void SetPhone(string pPhoneNumber, int pAirtime, int pSms )

            {

                phoneNumber = pPhoneNumber;

                airTime = pAirtime >= 0 ? pAirtime : 0;

                sms = pSms >= 0 ? pSms : 0;

            }

        public string GetPhoneDetails() 

        { 

            return phoneNumber + "\tAir Time" + airTime + "\tsms";

        }

        public void Call (int callDuration)

        {

            airTime = airTime - callDuration;   

        }

        public bool SendSms()

        {

            bool flag = false;

            if(sms >= 1)

            {

                sms--;

                flag = true;

            }

                return flag;

        }

    }