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

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