There are 4 shapes on a 8x8 grid. Which shape is closest to the gray square 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 square at (1, 3)
Distance from target shape to green right_triangle at (3, 3): 2
Distance from target shape to purple trapezoid at (1, 4): 1
Distance from target shape to pink trapezoid at (0, 6): 4
Closest shape is the purple trapezoid at (1, 4) with distance 1</think>

<answer>(1, 4)</answer>