
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
Starting from "1," using a calculator with only the [ +1 ] and [ x2 ] keys, find the fewest number of keystrokes needed to reach "400," ensuring the display shows "50" at least once during the sequence.

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