Visitors to Brazil must obtain a visa from a Brazilian Consulate (in some cases, Embassy) unless they come from a visa exempt country. More information can be found here.
In case of doubts we strongly recommend you to check with your local Brazilian diplomatic mission if you need to apply for a tourist visa beforehand.
Important: bear in mind that you must apply for a visa in advance, it might take some weeks or months for you to get it.
The Local Organizing Committee can provide a letter of invitation if you need to present it for visa or academic purposes. The Invitation Letter from CNPEM may NOT be enough to obtain a Brazilian visa.
Note: your passport must be valid for at least 6 months beyond your planned date of departure from Brazil.