There are 4 shapes on a 8x8 grid. Which shape is closest to the yellow 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: yellow right_triangle at (4, 6)
Distance from target shape to brown right_triangle at (2, 0): 8
Distance from target shape to purple right_triangle at (6, 3): 5
Distance from target shape to cyan square at (4, 0): 6
Closest shape is the purple right_triangle at (6, 3) with distance 5</think>

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