  A first study of numerical Monte Carlo simulations with two quark doublets, a
mass-degenerate one and a mass-split one, interpreted as u, d, s and c quarks,
is carried out in the framework of the twisted mass Wilson lattice formulation.
Tuning the bare parameters of this theory is explored on 12^3x24 and 16^3x32
lattices at lattice spacings a=0.20fm and a=0.15fm, respectively.
