I claim the answer is $38$. For $n = 6k$ , we divide in $2$ cases: $n = 12k$ ($k \ge 2$) Then take $6k-3$ and $6k+3$. $n = 12k+6$ ($k \ge 2$) Then take $6k-3$ and $6k+9$. If $n = 6k+2$ ($k \ge 7$) take $35$ and $6k-33$ If $n = 6k+4$ ($k \ge 5$) We take $25$ and $6k - 21$ Therefore, minimum $38$.

Sorry,is unclear! How to find 38?

soryn wrote: Sorry,is unclear! How to find 38? Trial and error. Try all even numbers from 20 to 50 and find a pattern. Then prove it.