For virtual screening using our docking program FITTED, a structure of 3CL pro co-crystallized to an αketoamide (PDB code: 6Y2G) and a structure of PL pro in complex with a ubiquitin aldehyde covalently bound to the catalytic cysteine (PDB code: 4MM3) were selected and the libraries mentioned above were docked in covalent docking mode keeping the other parameters to their default values.