  We address the problem of correcting a single error in an arbitrary discrete
memoryless channel with error-free instantaneous feedback. For the case of a
one-time feedback, we propose a method for constructing optimal transmission
strategies. The obtained result allows us to prove that for a binary channel,
two feedbacks are sufficient to transmit the same number of messages as in the
case of complete feedback. We also apply the developed techniques to a binary
asymmetric channel to construct transmission strategies for small lengths.
