There are 4 shapes on a 7x7 grid. Which shape is closest to the gray 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: gray square at (6, 6)
Distance from target shape to yellow rectangle at (0, 6): 6
Distance from target shape to purple rectangle at (6, 0): 6
Distance from target shape to blue right_triangle at (0, 4): 8
Closest shape is the yellow rectangle at (0, 6) with distance 6</think>

<answer>(0, 6)</answer>