
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
Given that $\overrightarrow{i}$ and $\overrightarrow{j}$ are two mutually perpendicular unit vectors, $\overrightarrow{a} = \overrightarrow{i} - 2\overrightarrow{j}$, $\overrightarrow{b} = \overrightarrow{i} + \lambda\overrightarrow{j}$, and the angle between $\overrightarrow{a}$ and $\overrightarrow{b}$ is acute, find the range of the real number $\lambda$.

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