There are 4 shapes on a 6x6 grid. Which shape is closest to the brown 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: brown rectangle at (4, 1)
Distance from target shape to green right_triangle at (5, 3): 3
Distance from target shape to red rectangle at (3, 4): 4
Distance from target shape to cyan trapezoid at (3, 5): 5
Closest shape is the green right_triangle at (5, 3) with distance 3</think>

<answer>(5, 3)</answer>