using System;

public class Program

{

    public static void Main()

    {

        int n,s ;

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

        int [] numbers = new int [n];

        for (int i = 0;i<n;i++)

        {

            numbers [i]= int.Parse(Console.ReadLine());

            }

          s = numbers[2]+ numbers[3];  

        Console.WriteLine("sum ="+ s); 

    }   

​

}