Like- and unlike-sign (left) and the like-sign-subtracted (right) invariant massdistribution of K$^0_{\rm S}$K$\pi$ triplets in $|y| < $ 0.5 in minimum-bias pp collisions at $\sqrt{s}$ = 13 TeV. The subtracted distribution is fitted with the function defined by Eq.1, and the dotted blue line describes the residual background distribution, which is given by Eq.2.