AT-OEMO-BEG 2019 Problem 2

A square $ABCD$ is given. Over the side $BC$ draw an equilateral triangle $BCS$ on the outside. The midpoint of the segment $AS$ is $N$ and the midpoint of the side $CD$ is $H$ . Prove that $\angle NHC = 60^o$ . . (Karl Czakler)