There are 3 shapes on a 6x6 grid. Which shape is closest to the blue 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: blue right_triangle at (5, 5)
Distance from target shape to green trapezoid at (0, 0): 10
Distance from target shape to brown rectangle at (1, 3): 6
Closest shape is the brown rectangle at (1, 3) with distance 6</think>

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