struct Node {
  std::size_t up, down, left, right;
  std::size_t row, col;

  Node(std::size_t _up = 0,
       std::size_t _down = 0,
       std::size_t _left = 0,
       std::size_t _right = 0,
       std::size_t _row = 0,
       std::size_t _col = 0)
    : up(_up), down(_down), left(_left), right(_right), row(_row), col(_col) {}
};