There are 6 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 (1, 3)
Distance from target shape to orange trapezoid at (2, 1): 3
Distance from target shape to brown right_triangle at (3, 3): 2
Distance from target shape to purple right_triangle at (0, 3): 1
Distance from target shape to blue right_triangle at (0, 2): 2
Distance from target shape to red right_triangle at (2, 0): 4
Closest shape is the purple right_triangle at (0, 3) with distance 1</think>

<answer>(0, 3)</answer>