using System;

public class Program

{

     public static chitiet hoadonmax(donhang donhang)

        {

            chitiet[] cts = donhang.chitiets;

            int max = 0;

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

            {

                if (cts[i].soluong * cts[i].dongia < cts[i+1].soluong * cts[i+1].dongia)

                {

                    max = i + 1;

                }

            }

            return cts[max];

        }

    public static void Main()

    {

         donhang dh = new donhang

            {

                tenkhach = "ko tra tien",

                chitiets = new chitiet[] { 

                    new chitiet {tenhang="Chuoi",soluong = 10, dongia= 2000 } ,

                    new chitiet {tenhang="Tao",soluong = 20, dongia= 1000 },

                    new chitiet {tenhang="Nho",soluong = 30, dongia= 5000 }

                }

            };

            var ct = hoadonmax(dh);

            Console.WriteLine(ct.tenhang);

    }

}

public struct donhang

    {

        public string tencuahang;

        public string tenkhach;

        public chitiet[] chitiets;

    }

 public   struct chitiet

    {

        public string tenhang;

        public int soluong;

        public int dongia;

    }