namespace Polygon

{

    public class Polygon

    {

        //Variable

        public int n;

        public XL_point [] A;

        // Function

        public void Input(string S)

        {

            Console.WriteLine(S);

            Console.Write("Nhap so dinh da giac: ");

            this.n = int.Parse(Console.ReadLine());

            this.A = new XL_point[n];

            for (int i = 0; i<A.Length; i++)

            {

                this.A[i] = new XL_point();

                this.A[i].Input($"Nhap đinh {i}");

            }    

        }

​

        public double Perimeter ()

        {

            double result = 0;

            result = this.A[0].Distance(this.A[A.Length-1]);

            for (int i = 0; i<this.A.Length-1; i++)

            {

                result = result + this.A[i].Distance(this.A[i + 1]);

            }    

            return result;

        }

    }

}

​

public class Program

{

    static void Main()

    {

        Polygon X = new Polygon();

        X.input();

        double perimeter = X.Perimeter();

        Console.WriteLine($"{perimeter}");

    }

}