  A combined search for standard model four-top-quark production in the single
lepton plus jets and dilepton channels will be presented. The analysis utilises
the 2015 dataset recorded by the CMS experiment at sqrt(s) = 13 TeV which
corresponds to an integrated luminosity of 2.6 fb-1. A scheme based on a
boosted decision tree algorithm is used to select signal and suppress
backgrounds. An upper limit on the cross section of four-top-quark production
will be presented.
