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class Solution {
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 public:
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  unordered_map<int, int> table;
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  int y, x;
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  Solution(int m, int n) {
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    y = m, x = n;
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  }
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  vector<int> flip() {
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    int Y = rand() % y, X = rand() % x, id;
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    while (table.count(id = (Y << 14) + X)) {
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      if (++X == x) X = 0, Y++;
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      if (Y == y) Y = 0;
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    }
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    table[id] = 1;
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    return {Y, X};
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  }
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  void reset() {
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    table.clear();
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  }
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};