There are 3 shapes on a 8x8 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, 5)
Distance from target shape to green trapezoid at (7, 1): 10
Distance from target shape to blue right_triangle at (3, 3): 4
Closest shape is the blue right_triangle at (3, 3) with distance 4</think>

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