There are 4 shapes on a 8x8 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, 7)
Distance from target shape to yellow rectangle at (7, 1): 13
Distance from target shape to cyan rectangle at (1, 3): 5
Distance from target shape to red rectangle at (4, 2): 9
Closest shape is the cyan rectangle at (1, 3) with distance 5</think>

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