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using System;

namespace Factorielle
{
    class Program
    { 
        // Implémentation récursive de la fonction factorielle
        static long FactRect(long value)
        {
            if (value == 0) return 1;
            return value * FactRect(value - 1);
        }

        // Implémentation itérative de la fonction factorielle
        static long Fact(long value)
        {
            long accumulator = 1;
            while( value > 1 )
            {
                accumulator *= value--;
            }
            return accumulator;
        }

        // Point d'entrée du programme
        static void Main(string[] args)
            Console.WriteLine("0! == " + FactRect(0));
            Console.WriteLine("1! == " + FactRect(0));
            Console.WriteLine("5! == " + FactRect(0));
            Console.WriteLine("6! == " + FactRect(0));

            Console.WriteLine("0! == " + Fact(0));
            Console.WriteLine("1! == " + Fact(0));
            Console.WriteLine("5! == " + Fact(0));
            Console.WriteLine("6! == " + Fact(0));
        }
    }
}