A common mass function. Panels a–c: normalized stacked MFs for young (log(Age/t_rh)≤0.2), intermediate (0.2 < log(Age/t_rh) < 0.75), and old clusters (log(Age/t_rh)≥0.75). The normalization choice is described in Sect. 3.2. Blue and azure solid lines represent the straight line best-fit of the low-mass (M ≤ 1 M_⊙) and high-mass (M > 1 M_⊙) stars, respectively. The derived slope is indicated in the bottom-left legends. Panel d: same as panels a–c, but for the whole sample of analyzed clusters.