Estimated positions of HD 181231 (log T_eff = 4.155) and HD 175869 (log T_eff = 4.079) on the log T_eff − log g plane (black dots) with evolutionary tracks of M/M_⊙ = 3,4,5,6,7 with a standard chemical composition of (X,Z) = (0.07, 0.02). Dotted lines are the evolutionary tracks of M/M_⊙ = 4,4.5,5,5.5,6 with a convective-core overshooting of 0.35H_p. There is no rotation included in these tracks. Open squares and circles indicate the positions of models for HD 181231 and HD 175869, respectively (see below).