There are 4 shapes on a 6x6 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 (2, 1)
Distance from target shape to cyan right_triangle at (5, 1): 3
Distance from target shape to yellow right_triangle at (5, 4): 6
Distance from target shape to brown trapezoid at (1, 5): 5
Closest shape is the cyan right_triangle at (5, 1) with distance 3</think>

<answer>(5, 1)</answer>