Manhattan Rectangle

**This is an interactive problem.** Chef has a secret rectangle. The sides of this rectangle are aligned with Cartesian axes $x$ and $y$. Let's denote the coordinates of the lower left corner of the rectangle by $(x_l, y_l)$ and the coordinates of the upper right corner by $(x_u, y_u)$; it is guaranteed that $x_l, y_l, x_u, y_u$ are non-negative integers. Your task is to find these coordinates.