Torque from the hydrodynamical and N-body simulations vs. the semi-major axes of the planet for the inner (top) and outer planet (bottom) in 2p20 DZ model. The grey lines denote the torque calculated from the formulae used in the N-body code as a function of distance from the star for a circular (solid) and an eccentric (dashed) planet. The values of the used eccentricities equal those of the hydrodynamical simulation after equilibrium. Comparison of the grey lines and the outputs of the simulations shows that these formulae are capable of correctly calculating the torque only for the outer planet before it approaches the transition zone.