There are 3 shapes on a 7x7 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 (3, 6)
Distance from target shape to purple square at (5, 1): 7
Distance from target shape to pink rectangle at (1, 3): 5
Closest shape is the pink rectangle at (1, 3) with distance 5</think>

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