There are 6 shapes on a 8x8 grid. Which shape is closest to the brown rectangle in terms of Manhattan distance? The final answer is the grid position of the closest shape like (row_index, column_index).
<think>Target shape: brown rectangle at (6, 3)
Distance from target shape to yellow right_triangle at (6, 4): 1
Distance from target shape to purple right_triangle at (0, 7): 10
Distance from target shape to cyan square at (1, 6): 8
Distance from target shape to blue square at (1, 0): 8
Distance from target shape to gray rectangle at (0, 3): 6
Closest shape is the yellow right_triangle at (6, 4) with distance 1</think>

<answer>(6, 4)</answer>