  For three given probability distributions describing positions of three
classical coins the quantum density matrix of spin-$1/2$ state is constructed
and its matrix elements are associated with triada of Malevich's squares. The
superposition principle of spin-$1/2$ states is presented in the form of
nonlinear addition rule for these classical coin probabilities. We illustrate
the formulas by the statement"God does not play dice - God plays coins".
