using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("He phuong trinh dang: a*x*x + b*x + c = 0");

            Console.Write("Nhap a: ");

            double a;

            a = double.Parse(Console.ReadLine());

            Console.Write("Nhap b: ");

            double b;

            b = double.Parse(Console.ReadLine());

            Console.Write("Nhap c: ");

            double c;

            c = double.Parse(Console.ReadLine());

            double d = (b * b) - (4 * a * c);

            if (d < 0)

            {

                Console.WriteLine("He phuong trinh tren vo nghiem");

            }

            else

            {

                if (d == 0)

                {

                    double x = (-b) / (2 * a);

                    Console.WriteLine("He phuong trinh co nghiem kep la: {0}", x);

                }

                else

                {

                    double x1 = ((-b) + Math.Sqrt(d)) / (2 * a);

                    double x2 = ((-b) - Math.Sqrt(d)) / (2 * a);

                    Console.WriteLine("He phuong trinh co 2 nghiem:");

                    Console.WriteLine("x1 = {0}", x1);

                    Console.WriteLine("x2 = {0}", x2);

                }

            }

            Console.ReadLine();

    }

}