[Swift] 콜라츠 추측

import Foundation

func solution(_ num:Int) -> Int {
    
    var number = num
    
    if number == 1 {
        return 0
    }
    
    for i in 1..<500 {
        if number % 2 == 0 {
            number = number / 2
        }else {
            number = number * 3 + 1
        }
        
        if number == 1 {
            return i
        }
    }
    
    return -1
}