There are 3 shapes on a 6x6 grid. Which shape is closest to the gray 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: gray right_triangle at (0, 4)
Distance from target shape to green right_triangle at (1, 3): 2
Distance from target shape to blue right_triangle at (1, 1): 4
Closest shape is the green right_triangle at (1, 3) with distance 2</think>

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