There are 5 shapes on a 7x7 grid. Which shape is closest to the yellow 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: yellow right_triangle at (3, 6)
Distance from target shape to purple square at (5, 2): 6
Distance from target shape to gray rectangle at (1, 4): 4
Distance from target shape to brown right_triangle at (4, 3): 4
Distance from target shape to blue right_triangle at (1, 0): 8
Closest shape is the gray rectangle at (1, 4) with distance 4</think>

<answer>(1, 4)</answer>