What do girls think about guys' butts?

i was wondering what girls really think about a guy's butt. I had never really thought about it but I heard a rumor that girls like asses too. Is this true or only certain girls? Sometimes girls I know pinch my butt and I thought it was playful but could they be aroused?

Lastly, my other experience was when I bent over to get something from my locker in my slim pants and a bunch were giggling and wouldn't say why. (sorry if this made me sound like a D-bag)
What do girls think about guys' butts?
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