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

class MyClass
{
    public static long DigitSum(long n)
    {
        if (n < 10)
        {
            return n;
        }
        else
        {
            return n.ToString().ToCharArray().Select(y => long.Parse(y.ToString())).Sum();
        }
    }

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

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