What freon is used on an 01 Lexus IS 300?

[01Lexi300]

I just got this car not that long ago, my AC was super cold until about a week ago. Only hot air comes out now. I was told to buy freon but I'm not sure what to buy.. any suggestions ? 

[1990LS400]

Fixing this is probably involves more than just adding refrigerant.  It's likely that a component has failed causing a leak.  If you have to ask what refrigerant to use, I suspect that you do not have the special tools and knowledge required to diagnose and repair A/C systems.