There are 6 shapes on a 4x4 grid. Which shape is closest to the gray 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: gray rectangle at (1, 2)
Distance from target shape to blue rectangle at (1, 0): 2
Distance from target shape to cyan right_triangle at (1, 3): 1
Distance from target shape to green trapezoid at (3, 1): 3
Distance from target shape to purple rectangle at (1, 1): 1
Distance from target shape to pink right_triangle at (0, 1): 2
Closest shape is the cyan right_triangle at (1, 3) with distance 1</think>

<answer>(1, 3)</answer>