using System;
using System.Text;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using static System.Console;
using static System.Math;

namespace YukiCoder
{
    public class Program
    {
        public static void Main(string[] args)
        {
            new Program().Solve();
        }

        public void Solve()
        {
            int n = int.Parse(ReadLine());
            int[] p = Console.ReadLine().Split().Select(x => int.Parse(x)).ToArray();

            int k = 1;
            for (int i = 0; i < n; i++)
            {
                k *= p[i];
            }
            
            while (k.ToString().Length != 1)
            {
                int sum = 0;
                for (int i = 0; i < k.ToString().Length; i++)
                {
                    sum += int.Parse(k.ToString()[i].ToString());
                }

                k = sum;
            }
            
            WriteLine(k);
        }
    }
}