There are 5 shapes on a 8x8 grid. Which shape is closest to the gray 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: gray right_triangle at (5, 5)
Distance from target shape to pink rectangle at (6, 3): 3
Distance from target shape to purple square at (3, 4): 3
Distance from target shape to yellow right_triangle at (4, 2): 4
Distance from target shape to orange rectangle at (1, 7): 6
Closest shape is the pink rectangle at (6, 3) with distance 3</think>

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