
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
Let $D$ be on side $BC$ of $\triangle ABC$, with $BD= \frac {1}{3}BC$. If $\overrightarrow{AD}=\lambda_{1} \overrightarrow{AB}+\lambda_{2} \overrightarrow{AC}$ ($\lambda_{1},\lambda_{2}$ are real numbers), then the value of $\lambda_{1}+\lambda_{2}$ is ______.

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