At a campaign event last October, McCain joked that Jack needed a "DNA check" because he had yet to receive a single demerit. (Jack McCain told GoMids.com that he did accumulate some demerits -- for wearing flip-flops outside and forgetting to shave).

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Some, like Conlin, label these flip-flops and accuse Giuliani of political calculation.

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You will also be given some shoes by your attendant - either traditional wooden clogs or fluorescent flip-flops.

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Rangers say some visitors partake in dangerous practices such as hiking treacherous trails in flip-flops, climbing over safety rails to take better pictures or swimming perilously close to waterfalls.

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Crocs, which have some structure, cushion and breathability, can be an easy alternative to flip-flops, while sandals with a substantial foot bed and softer and broader straps are also a better option, Oswell said.

CNN: Flip-flops present feet with a painful problem

But the rubber soles of most flip-flops just bend all over the place, while the stiff soles of some stylish varieties may not bend at all, she said.

CNN: Flip-flops present feet with a painful problem