Awaiting for a separate article about a sum of several numbers.

I don't see why this is useful.

I think it's useful because it's often requested in contests, and it's not very obvious.

We can simply have a sentence saying gcd is associative, so we can define gcd(a, b, c) as gcd(a, gcd(b, c)) and so forth.
The code is trivial.

Indeed.

If we're adding this, I think it's worthwhile to mention that finding $\gcd(a_1,\dots,a_n)$ where $a_i \leq C$ with Euclidean algorithm would take $O(n + \log C)$, rather than $O(n \log C)$, as every non-trivial iteration of the Euclidean algorithm reduces the current GCD candidate by at least a factor of $2$. But this part is better to add at the end of the "time complexity" section.

Preview the changes for PR #1355 (for commit 38982cb) at https://gh.cp-algorithms.com/1355/.

Preview the changes for PR #1355 (for commit cbb7b39) at https://gh.cp-algorithms.com/1355/.

Thanks! And sorry for repeated merges of main into patch-1, I needed to check how pull requests preview work.