using System;

​

public class Program

{   

    public static bool isTriangle (double s1, double s2, double s3) {

        bool check = true; //assume triangle can be formed

​

        //false check

        if (s1>s2+s3 || s2>s1+s3 || s3>s1+s2)

            check = false;

​

        return check;

    }

​

    public static void Main()

    {

        Console.WriteLine("Welcome to Triangle Properties.");

​

        double s1=0;

        double s2=0;

        double s3=0;  //three side lengths

​

        do{

            if (s1<0)  //error messages for negative side lengths

                Console.WriteLine("Side 1 must be positive.");

            if (s2<0)

                Console.WriteLine("Side 2 must be positive.");

            if (s3<0)

                Console.WriteLine("Side 3 must be positive.");

            Console.WriteLine("Enter in side 1:");  //takes in length 1

            s1=Convert.ToDouble(Console.ReadLine());

​

            Console.WriteLine("Enter in side 2:");

            s2=Convert.ToDouble(Console.ReadLine());

​

            Console.WriteLine("Enter in side 3:");

            s3=Convert.ToDouble(Console.ReadLine());

            if(!isTriangle(s1,s2,s3)) //error message for non triangle

                Console.WriteLine("Triangle cannot be formed with given sides!");

        }while (s1<0 || s2<0 || s3<0|| !isTriangle(s1,s2,s3));  //error check to ensure sides are positive and triangle can be formed

​

​

        Console.WriteLine("Sides of triangle:"+s1+", "+s2+", "+s3);

​

​

    }

}