Mass spectrum (multiplied by m² to provide a proxy for a cumulative mass distribution in the system) at four different times indicated on the panels, expressed in units of collisional timescale for the initial mass bin. We use ﹩\tilde{m}﹩ and ﹩\tilde{N}﹩ for m and N, normalized by the initial mass (m = 1) and initial number of objects in the system. Different-colored curves correspond to different numbers of bins in the simulation, labeled in panel (a). Solid lines correspond to the curves from the ﹩{ \mathcal O }\left({N}^{2}\right)﹩ algorithm, and dotted lines to those from the ﹩{ \mathcal O }\left({N}^{3}\right)﹩ algorithm. In the bottom right panel, we show in black the line of slope 1/6 (consistent with Dohnanyi 1969), which provides a good overall fit to the fragment distribution. The superimposed wavy structure is discussed in the text.