Tickets for a certain park are 10 yuan per person, and more than 30 people (including 30 people) can buy group tickets with a 30% discount, that is, 7 yuan per person. Buying a group ticket is cheaper than buying an ordinary ticket for the minimum number of people.
某公园的门票是每人10元，30人以上(含30人)可以买团体票，按7折优惠，即每人7元．最少多少人时买团体票比买普通票便宜．
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