Help! Chem homework!

ok so there's this question...

Consider the gaseous equilibrium 2A ? 2B + C. Four moles of A are put into a one-L flask. At equilibrium, the flask is found to contain 1.0 mole of C. Calculate the value for the equilibrium constant.

I know how to do this if the equation is filled with actual elements/compounds, but I get so confused when I look at this one. Does the 2 before the A mean the number of moles? What about the given where it says that there are 4 moles of A, do I have to multiply them or something?

Please help!