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, 1)
Distance from target shape to pink trapezoid at (1, 5): 7
Distance from target shape to blue square at (5, 5): 5
Distance from target shape to green right_triangle at (0, 3): 6
Closest shape is the blue square at (5, 5) with distance 5</think>

<answer>(5, 5)</answer>