There are 6 shapes on a 9x9 grid. Which shape is closest to the purple right_triangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: purple right_triangle at (5, 1)
Distance from target shape to blue right_triangle at (3, 1): 2
Distance from target shape to yellow trapezoid at (8, 7): 9
Distance from target shape to brown right_triangle at (6, 8): 8
Distance from target shape to gray rectangle at (0, 7): 11
Distance from target shape to green square at (7, 4): 5
Closest shape is the blue right_triangle at (3, 1) with distance 2</think>

<answer>(3, 1)</answer>