13. We use $A, B, C, D, E$ to represent the number of gold coins held by students 甲, 乙, 丙, 丁, 戊, respectively. The total number of these gold coins is denoted by $n$, which means $n=A+B+C+D+E$. It is known that:
(1) $A, B, C, D, E$ are all greater than or equal to 1;
(2) $A<B<C<D<E$;
(3) Each of the five students knows the value of $n$ and the number of gold coins they hold;
For a certain $n$, if there exists a distribution of gold coins (once the total number of gold coins is fixed, the number of gold coins each person holds can be allocated according to the above requirements) such that no student can guess the number of gold coins everyone holds, then $n$ is called a "central number". Find: the smallest "central number".
【Answer】19