What is the best jailbreaking program for the iPhone 4 iOS 6.1.3?

Hi, I want to jailbreak my iPhone 4 (iOS 6.1.3). I have been having some trouble finding a good program that works. Any suggestions? Also, please refer me to some websites where you can download the program. I have tried redsnow and it doesn't work.

There are no known jailbreaks for iOS 6.1.3.