using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("saisir un nombre");

        int n = Convert.ToInt32(Console.ReadLine());

        int fact = 1;

        for( int i = 1; i <=n; i=i+1)

        {

            fact = fact*i;  

        }

        Console.WriteLine(fact);

    }

}

​

​