Show that the series is convergent?

Question

$a_n=(1+\frac{1}{n})^n$ and $n\geq 1$ I check first $n\to \infty$ then $\lim_{n\to \infty}=(1+\frac{1}{\infty})^\infty$ $=(1+0)^\infty=1^\infty$ I don't find the next step.Help me