There are 4 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 (3, 7)
Distance from target shape to cyan rectangle at (0, 0): 10
Distance from target shape to pink trapezoid at (4, 1): 7
Distance from target shape to gray right_triangle at (7, 5): 6
Closest shape is the gray right_triangle at (7, 5) with distance 6</think>

<answer>(7, 5)</answer>