There are 3 shapes on a 4x4 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 (3, 1)
Distance from target shape to yellow rectangle at (0, 0): 4
Distance from target shape to red trapezoid at (3, 3): 2
Closest shape is the red trapezoid at (3, 3) with distance 2</think>

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