using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;
using System.Numerics;

class MyClass
{
    public static int DigitSum(BigInteger n)
    {
        if (n < 10)
        {
            return (int)n;
        }
        else
        {
            BigInteger dsum = 0;
            while (n > 0)
            {
                dsum += n % 10;
                n /= 10;
            }
            return DigitSum(dsum);
        }
    }

    public static void Solve()
    {
        var N = int.Parse(Console.ReadLine());
        var P = Console.ReadLine().Split().Select(BigInteger.Parse).ToArray();
        BigInteger prod = 1;
        foreach (var item in P)
        {
            prod *= item;
            prod = DigitSum(prod);
        }
        Console.WriteLine(DigitSum(prod));
    }

    public static void Main()
    {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        Console.SetOut(sw);
        Solve();
        Console.Out.Flush();
    }
}