There are 6 shapes on a 6x6 grid. Which shape is closest to the red 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: red right_triangle at (1, 3)
Distance from target shape to blue rectangle at (5, 1): 6
Distance from target shape to pink right_triangle at (3, 5): 4
Distance from target shape to brown trapezoid at (2, 1): 3
Distance from target shape to purple square at (0, 0): 4
Distance from target shape to orange square at (0, 1): 3
Closest shape is the brown trapezoid at (2, 1) with distance 3</think>

<answer>(2, 1)</answer>