Definition: In this task, you are given a Reddit post as a text. Your task is to generate a title for this text. The title should start with "TIFU by", followed by a situation that caused humor. The title should contain 7-12 words, ideally.
Input: Text: this didn't happen today but this weekend. i went camping with my girlfriend, her twin sister, older sister and friend we started drinking and it was my first time getting drunk in my drunken haze i see what i thought was my girlfriend and out of habit slapped her ass and then her older sister turns around to my horror and says magnus just slapped my ass, both my girlfriend and her sister were wearing grey shirts and at the moment i thought it was my girlfriend. everyone just laughed but i feel bad haha

Tifu by drinking for the first time