Show that in a finite abelian group $G=\{a_1,\dots, a_n\}$, and $x=a_1\dots a_n$, then $x^2=e$

Question

Let $G=\{a_1, a_2, \dots, a_n\}$ be a finite abelian group and $x=a_1a_2\dots a_n$. Then show that $x^2=e$.

Let $a_i\in G$, then $a^{-1}_i\in G$. Suppose $a_i^{-1}=a_j$. How can show the required result?