 	{
 		for i in range
 		{
-			letters.append(String(UnicodeScalar(i)))
+			letters.append(String(describing: UnicodeScalar(i)))
 		}
 	}
 

enum LetterSet
{
	case lowerCase
	case UpperCase
	case Numbers
	case SpecialSymbols
	case All

}

func randomString(length: Int, letterSet: LetterSet...) -> String
{
	var letters = [String]()
	var ranges = [Range<Int>]()

	for ele in letterSet
	{
		switch ele
		{
		case .All:
			ranges.append(33...126)

		case .Numbers:
			ranges.append(48...57)

		case .lowerCase:
			ranges.append(97...122)

		case .UpperCase:
			ranges.append(65...90)

		case .SpecialSymbols:
			ranges += [33...47, 58...64, 91...96, 123...126]
		}
	}

/**
	Returns the n-th prime number.
*/
func getPrime(_ n: Int) -> Int
{
	precondition(n > 0, "There is no 0-th prime number")

	var prime = 2
	var primeCount = 1
