1. At every non-hydrogen atom, extract all circular substructures up to the specified maximum radius as isomeric, canonical SMILES. Isomeric information ("@" and "@@" characters) is manually removed from the extracted SMILES, while the implicit E/Z-isomerism ("/", and "\" characters) are maintained. Allene chirality and conformational chirality such as in biaryls or in helicenes are not considered, as they cannot be specified in the SMILES notation. Radius 0 is skipped.