Same event, mixed event, signal from data, and MC true signal invariant mass distributions of ${\rm \overline{n}}\pi^+$ (top row) and ${\rm \overline{n}}\pi^-$ (bottom row) pairs in pp (left column) and p--Pb (right column) collisions for two selected $p_{\rm{T}}$ bins. Solid and dashed vertical lines represent integration ranges at 1/4 and 1/3 of the maximum, respectively. The PYTHIA 8  and DPMJET 3.0-5  event generators were used for Monte-Carlo simulations.