func wallpaper(length: Double, width: Double, height: Double) -> String {

    let numberOfRolls = [0: "zero",
               1: "one",
               2: "two",
               3: "three",
               4: "four",
               5: "five",
               6: "six",
               7: "seven",
               8: "eight",
               9: "nine",
               10: "ten",
               11: "eleven",
               12: "twelve",
               13: "thirteen",
               14: "fourteen",
               15: "fiveteen",
               16: "sixteen",
               17: "seventeen",
               18: "eighteen",
               19: "nineteen",
               20: "twenty"
    ]

    guard length != 0.0 && width != 0.0 && height != 0.0 else {
        return numberOfRolls[0]!
    }

    var amount = 0.0
    [length, width].forEach {
        amount += (($0 / 0.52) / ( 10.0 / height)) * 2
    }
    let total = Int((amount * 1.15).rounded(.up))

    return numberOfRolls[total] ?? numberOfRolls[0]!
}

wallpaper(length: 0.0, width: 3.5, height: 3.0)
wallpaper(length: 4.0, width: 3.5, height: 3.0)
wallpaper(length: 6.3, width: 4.5, height: 3.29)
wallpaper(length: 7.8, width: 2.9, height: 3.29)
wallpaper(length: 6.3, width: 5.8, height: 3.13)
wallpaper(length: 6.1, width: 6.7, height: 2.81)