There are 6 shapes on a 4x4 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, 2)
Distance from target shape to gray square at (0, 2): 3
Distance from target shape to brown square at (1, 0): 4
Distance from target shape to yellow right_triangle at (3, 1): 1
Distance from target shape to orange right_triangle at (0, 0): 5
Distance from target shape to red rectangle at (2, 2): 1
Closest shape is the yellow right_triangle at (3, 1) with distance 1</think>

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