  We develop a way of improving complex Langevin dynamics motivated by the
Lefschetz-thimble decomposition of integrals. In our method, arbitrary
observables of an original model with multiple Lefschetz thimbles are computed
by a modified model with a single thimble. We apply our modification method to
a one dimensional integral in which the naive implementation of the complex
Langevin dynamics fails to reproduce the exact results due to the severe sign
problem. We show that the toy model can be modified so that the new model
consists of a single Lefschetz thimble. We find that correct results can be
obtained by the improved complex Langevin dynamics.
