
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
A triangular grid is made of cord, which can burn. The fire spreads along the cord at the same speed in all directions (each segment burns exactly in 1 minute). Which of the marked segments (AB, BC, CD, DE, or AF) of the grid will burn last if the grid is ignited at point O? How long will they take to burn?

Present the answer in LaTex format: \boxed{Your answer}
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