There are 6 shapes on a 8x8 grid. Which shape is closest to the green 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: green rectangle at (2, 1)
Distance from target shape to blue rectangle at (6, 5): 8
Distance from target shape to brown square at (4, 4): 5
Distance from target shape to red square at (1, 6): 6
Distance from target shape to yellow rectangle at (4, 6): 7
Distance from target shape to cyan right_triangle at (7, 6): 10
Closest shape is the brown square at (4, 4) with distance 5</think>

<answer>(4, 4)</answer>