There are 3 shapes on a 10x10 grid. Which shape is closest to the green square in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: green square at (6, 6)
Distance from target shape to purple right_triangle at (3, 1): 8
Distance from target shape to red rectangle at (1, 8): 7
Closest shape is the red rectangle at (1, 8) with distance 7</think>

<answer>(1, 8)</answer>