View Compilation Error

0_0_3862296_13161.cpp: In function `int main()':
0_0_3862296_13161.cpp:17: error: could not convert `Q.std::priority_queue<_Tp, _Sequence, _Compare>::empty [with _Tp = std::pair<int, int>, _Sequence = std::vector<std::pair<int, int>, std::allocator<std::pair<int, int> > >, _Compare = std::less<std::pair<int, int> >]' to `bool'
0_0_3862296_13161.cpp:17: error: in argument to unary !