answer.code: In function ‘ull generate_base(ull)’:
answer.code:260:13: error: ‘gcd’ was not declared in this scope
  260 |         if (gcd(mod - 1, k) != 1) continue;
      |             ^~~
answer.code: In function ‘int main()’:
answer.code:425:22: error: missing template arguments before ‘rh’
  425 |         Rolling_Hash rh(a, base);
      |                      ^~
answer.code: In lambda function:
answer.code:430:18: error: ‘rh’ was not declared in this scope
  430 |                 (rh.get_hash(i, i + mid) == rh.get_hash(j, j + mid) ? ok : ng) = mid;
      |                  ^~
answer.code: In function ‘int main()’:
answer.code:450:23: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’ [-Wc++17-extensions]
  450 |             for (auto [tar, val] : addc[i])
      |                       ^