There are 6 shapes on a 7x7 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 (6, 1)
Distance from target shape to yellow right_triangle at (1, 5): 9
Distance from target shape to red rectangle at (6, 3): 2
Distance from target shape to cyan square at (5, 2): 2
Distance from target shape to pink right_triangle at (0, 1): 6
Distance from target shape to brown right_triangle at (6, 4): 3
Closest shape is the red rectangle at (6, 3) with distance 2</think>

<answer>(6, 3)</answer>