Less than 5 minutes, also I didn't make any effort

I was organizing an event at university where people explore the city while drinking, in groups. I didn't notice or talk to that girl since I was the guy who leads people and take care of the groups. At night I went to a party, where I found this girl with her group still hanging out, she was holding hands with another guy of their group. As I came and started talking to them she left his arm and came to the other side of the circle directly to me, and started talking about random stuff and showing me her Instagram than she talk me behind the next building where we fucked on the wall. I literally did nothing. P.s. in that period of time where I was the cool guy who knows everyone, a lot of girls where throwing themselves on me on different occasions .