// Determine a type of triangle by the length of its sides a, b, c.

// The program should input positive integers a, b, c and print 

// “rectangular”, “acute”, “obtuse”, or “impossible” accordingly.

​

using System;

using System.Diagnostics;

public class Program

{

    public static int InputInt(string prompt)

    {

        Console.Write("Enter " + prompt + ":");

        return Convert.ToInt32(Console.ReadLine());

    }

    public static void Main()

    {

        // input data

        int a = InputInt("length of side a");

        int b = InputInt("length of side b");

        int c = InputInt("length of side c");

        Trace.Assert(a > 0 && b > 0 && c > 0);

        if(c < a)

        {   // swap c,a; c increases

            int t = c; c = a; a = t;

        }

        /* original sides stored in a,b,c and c >= a  */

​

        if(c < b)

        {   // swap c,b; c increases

            int t = c; c = b; b = t;

        }

        /* original sides stored in a,b,c and c >= a and c>=b */

        // calculate

        if (a + b <= c){

            Console.Write("The sides cannot create a triangle!");   

        }else if (a * a + b * b > c * c) {

            Console.Write("It is an acute triangle");

        }else if (a * a + b * b == c * c) {

            Console.Write("It is a right triangle");

        }else{

            Console.Write("It is an obtuse triangle");

        }

    }

}