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class SeatManager {
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 public:
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  priority_queue<int, vector<int>, greater<int>> pq;
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  SeatManager(int n) {
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    for (int i = 1; i <= n; i++) pq.push(i);
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  }
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  int reserve() {
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    int top = pq.top();
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    pq.pop();
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    return top;
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  }
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  void unreserve(int seatNumber) {
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    pq.push(seatNumber);
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  }
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};