# Computing a scalar from UV coordinates in Cycles nodes

I have a .obj mesh loaded with given UV coordinates. I'd like to color the mesh using its UV coordinates, similarly to this image. I think the correct way is to first compute a scalar out of the uv coordinates, something like u*v, and then connect that scalar to the hue value of a HSV node. Thing is, I don't know which module can I use to take the UV Map's output and turn it into a scalar.