answer.code: In member function ‘bool rigidity_matroid::push(int, int, const bool&)’:
answer.code:46:30: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   46 |                         auto [u, t] = q[hd];
      |                              ^
answer.code:53:54: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   53 |                                                 auto [v, s] = pebble_from[id];
      |                                                      ^
answer.code: In member function ‘void rigidity_matroid::clear()’:
answer.code:76:61: error: missing template arguments before ‘{’ token
   76 |                 fill (pebble.begin (), pebble.end (), array { -1, -1 });
      |                                                             ^
answer.code:77:71: error: missing template arguments before ‘{’ token
   77 |                 fill (pebble_from.begin (), pebble_from.end (), array { -1, -1 });
      |                                                                       ^