  Recently three experiments reported a discovery of manifestly exotic
Z_c^+(3900) in the decay to J/psi pi+, while J and P are experimentally
unknown. We search for this state on the lattice by simulating the channel with
J^PC=1^+- and I=1, and we do not find a candidate for Z_c^+(3900). Instead, we
only find discrete scattering states D D* and J/psi pi, which inevitably have
to be present in a dynamical QCD. The possible reasons for not finding $Z_c^+$
may be that its quantum numbers are not $1^{+-}$ or that the employed
interpolating fields are not diverse enough. Simulations with additional types
of interpolators will be needed to reach a more definite conclusion.
