using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;


namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            var numRings = int.Parse(Console.ReadLine());
            var rings = new int[30];
            for (int i = 0; i < numRings; i++)
            {
                var input = int.Parse(Console.ReadLine());
                rings[input] += 1;
            }
            var sums = new List<int>();
            for (int i = 0; i < 30; i++)
            {
                if (rings[i] > 1)
                {
                    sums.Add(Factorial(rings[i]));
                }
            }
            var finalsum = 1;
            foreach (var item in sums)
            {
                if (item > 1)
                {
                    finalsum *= item;
                }
            }
            Console.WriteLine(finalsum);
        }
        static int Factorial(int i)
        {
            if (i <= 1)
                return 1;
            return i * Factorial(i - 1);
        }
    }
}