with fil.io ;
   use fil.io ;

   procedure factorielle is
      function factorial (n: natural)
      return positive is
      begin
         if n=0 then 
            return 1 ;
         else 
            return n * factorial(n-1) ;
         end if;
      end factorial ;
   
   
      n:natural;  
   begin 
   
      get(n);
      put(factorial(n)) ;
   
   end factorielle;