Same event, mixed event, signal from data, and MC true signal invariant mass distributions of ${\rm \overline{n}}\pi^+$ pairs in pp (left) and p$-$Pb (right) collisions for one selected $p_{\rm{T}}$ bin. Solid and dashed vertical lines represent integration ranges at 1/4 and 1/3 of the maximum, respectively. The PYTHIA 8 [29] and DPMJET 3.0-5 [30] event generators were used for Monte-Carlo simulations.