
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
The following three daily phenomena:<br/>① Using two nails to fix a wooden strip on the wall;<br/>② Straightening a curved road can shorten the distance;<br/>③ In physical education class, the teacher measures a student's long jump performance.<br/>Among them, the phenomenon that can be explained by "the shortest distance between two points is a straight line" is____$($fill in the number).

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