Euler polyhedron formula

The Euler polyhedron formula relates the number of faces, edges, and vertices of any polygon or planar graph. The formula is

$V-E+F=2$

where $$V$$ is the number of vertices, $$E$$ is the number of edges, and $$F$$ is the number of faces. For example, a cube has 8 vertices, 12 edges, and 6 faces.

Figure 1: The cube.

and $$8-12+6=2$$.