func ator(var n: Int) -> String {

    var result = ""

    for (value, letter) in
       [( 1000,    "M"),
        (  900,   "CM"),
        (  500,    "D"),
        (  400,   "CD"),
        (  100,    "C"),
        (   90,   "XC"),
        (   50,    "L"),
        (   40,   "XL"),
        (   10,    "X"),
        (    9,   "IX"),
        (    5,    "V"),
        (    4,   "IV"),
        (    1,    "I")]
    {
        while n >= value {
            result += letter
            n   -= value
        }
    }
    return result
}