3 We consider graphs with vertices colored black or white. "Switching" a vertex means: coloring it black if it was formerly white, and coloring it white if it was formerly black.
3 Isaalang-alang namin ang mga graph sa vertices kulay na itim o puti. "Lumipat" tuktok ng isang ibig sabihin nito: pangulay itim na ito kung ito ay dating puti, at pangkulay puti ito kung ito ay dating itim.