  The lateral distribution of muons with threshold energy e ~ 1*sec(theta) GeV
have been studied in showers with energy E>=10^17 eV. The data considered in
the analysis have been collected from November 2011 to June 2013. Experimental
values are compared to predictions obtained with the use of CORSIKA code within
the framework of various hadron interaction models. The best agreement between
experiment and theory is observed for QGSJETII-04 model. At E~10^17 eV it
complies to a mixed cosmic ray composition with the mean atomic number
<lnA>~3.0+/-0.5. At E>= 4*10^17 eV the composition varies around the value
<lnA>~0.5.
