proof writing - Prove the shift rule for series

Let $N$ be a natural number. Then the series $\sum_{n=1}^{\infty}a_n$ converges if and only if the series $\sum_{n=1}^{\infty}a_{N+n}$ converges.

I've tried splitting $\sum_{n=1}^{\infty}a_n$ into $\sum_{n=1}^{\infty}a_{N+n} +\sum_{n=1}^{N}a_n$ but am not getting anywhere. I've also tried using the $\epsilon$ definition for convergence but am getting confused.