%% Regression level = 0
%% Result = Valid
%% Runtime = 1
%% Language = presentation
OPTION "tcc" 0;

DATATYPE
  tree = node(left : tree, right : tree) | leaf
END;

x : tree;
z : tree;

QUERY NOT (left(left(left(left(left(left(left(left(left(left(z)))))))))) = x AND is_node(z) AND z = x);