answer.code: In function ‘int main()’:
answer.code:54:8: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’ [-Wc++17-extensions]
   54 |   auto [c, l, r, d] = parse1('#');
      |        ^
answer.code:55:8: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’ [-Wc++17-extensions]
   55 |   auto [t, l2, r2, d2] = parse1(c);
      |        ^
answer.code:84:17: error: ‘midpoint’ was not declared in this scope
   84 |         ll km = midpoint(kl, kr);
      |                 ^~~~~~~~
answer.code:101:17: error: ‘midpoint’ was not declared in this scope
  101 |         ll km = midpoint(kl, kr);
      |                 ^~~~~~~~