     let digits:[Int]
     let isNegative:Bool
     
-    init(value:String) {
+    init(value:String, negative:Bool = false) {
         isNegative = value[value.startIndex] == "-" ? true : false
         if isNegative {
             digits = value.characters.dropFirst().flatMap{Int(String($0))}

            return BigInteger(value: self.digits + value.digits)
        case .Negative:
            return BigInteger(value: self.digits + value.digits, negative:true)
        case .Different:
            print("Different")
        }
        return self
    }


addResult.description()

let subA = BigInteger(value: "54")
let subB = BigInteger(value: "21", negative: true)

let subResult = subA - subB
subResult.description()

