1. Pedro II School, Rio de Janeiro, RJ, Brazil. E-mail: alduboc@cp2.g12.br
2. Department of Computer Science, Institute of Computing, Universidade Federal Fluminense (UFF), Niterói, RJ, Brazil. E-mail: alinepaes@ic.uff.br
3. Department of Systems Engineering and Computer Science - COPPE, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ, Brazil. E-mail: gerson@cos.ufrj.br