Variation in the mass of nitrogen and oxygen in the outer layers of the star as a function of the Lagrangian mass taken as the lower limit of the integration. This lower limit can be called the mass of the remnant. The case of the rapidly rotating 20 M_⊙ model is shown. The vertical dashed grey line denotes the remnant mass adopted in the present paper, while the horizontal dashed grey line denotes the nitrogen yield. The dashed lighter grey line denotes the typical mass of an NS.