
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 the sequence $\{a_n\}$: $\frac {1}{2}$, $\frac {1}{3}+ \frac {2}{3}$, $\frac {1}{4}+ \frac {2}{4}+ \frac {3}{4}$, ..., $\frac {1}{10}+ \frac {2}{10}+ \frac {3}{10}+...+ \frac {9}{10}$, ..., if $b_n= \frac {1}{a_n \cdot a_{n+1}}$, find the sum of the first $n$ terms of the sequence $\{b_n\}$.

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