If an iron (III) complex with the formula [ Fe ( NH_3)_x ( CN )_y ]^- has no electron in its e_g orbital, then the value of x + y is

If an iron (III) complex with the formula $\displaystyle \left[\mathrm{Fe}\left(\mathrm{NH}_3\right)_{\mathrm{x}}(\mathrm{CN})_{\mathrm{y}}\right]^{-}$has no electron in its $\displaystyle \mathrm{e}_{\mathrm{g}}$ orbital, then the value of $\displaystyle \mathrm{x}+\mathrm{y}$ is