There are 6 shapes on a 4x4 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 (1, 3)
Distance from target shape to green rectangle at (2, 1): 3
Distance from target shape to pink rectangle at (2, 3): 1
Distance from target shape to cyan square at (1, 0): 3
Distance from target shape to yellow square at (3, 1): 4
Distance from target shape to blue right_triangle at (3, 0): 5
Closest shape is the pink rectangle at (2, 3) with distance 1</think>

<answer>(2, 3)</answer>