using System;

public class Program

{

    public static void Main()

    {

        int n; string s;

        s= Console.ReadLine();

        n = int.Parse(s);

        int sum = 1;

        for(int i=1; i<=n; i++)

        {

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

            if(i%2==0);

            sum= sum*x;

        }

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

    }

}