There are 5 shapes on a 5x5 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 (1, 3)
Distance from target shape to blue right_triangle at (2, 3): 1
Distance from target shape to red right_triangle at (0, 2): 2
Distance from target shape to yellow square at (0, 4): 2
Distance from target shape to pink rectangle at (4, 3): 3
Closest shape is the blue right_triangle at (2, 3) with distance 1</think>

<answer>(2, 3)</answer>