There are 5 shapes on a 6x6 grid. Which shape is closest to the red 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: red square at (5, 3)
Distance from target shape to gray trapezoid at (5, 1): 2
Distance from target shape to yellow rectangle at (1, 4): 5
Distance from target shape to purple trapezoid at (1, 5): 6
Distance from target shape to blue square at (3, 4): 3
Closest shape is the gray trapezoid at (5, 1) with distance 2</think>

<answer>(5, 1)</answer>