In these exercises you need to draw the chemical structure based on a molfile.
The molfiles are in version V2000 and the charge and isotope information are in respectively M CHG and M ISO. The information does not have to be repeated in the atom line.
M CHG 2 1 1 2 -1
Means that we have 2 information, atom 1 has charge +1 and atom 2 has charge -1