There are 6 shapes on a 6x6 grid. Which shape is closest to the purple right_triangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: purple right_triangle at (5, 1)
Distance from target shape to gray right_triangle at (2, 4): 6
Distance from target shape to green right_triangle at (4, 3): 3
Distance from target shape to pink right_triangle at (1, 0): 5
Distance from target shape to yellow rectangle at (0, 3): 7
Distance from target shape to brown square at (3, 0): 3
Closest shape is the green right_triangle at (4, 3) with distance 3</think>

<answer>(4, 3)</answer>