Stack of plots showing the evolution of free magnetic energy (top plot) and of the net, right- and left-handed helicity budgets (bottom plot) for each of the four major eruptive flares in AR11618 a few hours before and after the events. The first and second flares (M1.7 and M1.6, respectively) are shown in plots a, b while the last two flares (M1.4 and M3.5, respectively) are shown in plots c, d.