There are 4 shapes on a 6x6 grid. Which shape is closest to the gray rectangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: gray rectangle at (4, 0)
Distance from target shape to orange right_triangle at (0, 0): 4
Distance from target shape to red trapezoid at (1, 5): 8
Distance from target shape to green square at (4, 3): 3
Closest shape is the green square at (4, 3) with distance 3</think>

<answer>(4, 3)</answer>