Here's a lesson for the fellas: "nice bum" is not an adequate pick-up line. If you say this to a girl, she is unlikely to swoon and hand over her phone number. In fact, she will probably ignore you and pretend you do not exist. If this happens, do not walk over to her again 5 minutes later and repeat "nice bum". While the statement itself may be true, the sentiment is somewhat lacking. Next time, try "hello".