How to Pay Overstayed Visa Fine

Hi all, I overstayed my visa on my last trip to Brazil by a few days, and am heading back in a few weeks. I was told I can pay the fine on my way back into the country, and I intend to do so. I'm just trying to figure out where and how exactly I do this, so I'm prepared accordingly. I'm flying into Rio (GIG); can I pay directly at Immigration? Do I have to go to an authorized bank in the airport and have the payment certified? I'm flying in on a Sunday so I'm not sure that banks would be open to accept payment. If I can pay here somehow beforehand, I would do that. I looked around a decent bit and didn't find any up-to-date info, so if anybody has any, please let me know. Thanks a lot.