func fibo( n: Int ) -> Int { if n < 2 { return 1 } else { return fibo( n: n - 1 ) + fibo( n: n - 2 ) } } if CommandLine.arguments.count < 2 { print( "Ups!" ) } else { let arg = CommandLine.arguments[ 1 ] let argstr: Int? = Int( arg ) if argstr != nil { let argint: Int! = Int( arg ) print( fibo( n: argint ) ) } else { print( "Ups!" ) } }