Sex with 2 guys in one night?

So on saturday night i had a "sleepover" with my friend (guy A) who i have gotten with a few times, we didnt have sex but may aswell have. on sunday i found out i had sex with my other friend (guy B) and i have NO reccollection of it. I remember being with guy A at the end of the night and at that point i didnt even know i had been with guy B. the guys are friends and we all live together in a hostel. 1. Do i tell both of them or only one of them or none? 2. how bad is this on a scale of 1-10. 3. Any other hints on what the hell i do?????????? i have only been with 3 guys in my life - now 4 - over the past 3 years so im not a slut but just messed up. i had a whole bottle of vodka 40% and hadn't eaten all day so was wastttted. i have memorys of pre-drinks and then being with guy A at like 2am. Help