Y by David-Vieta
Let
denotes the set of integers from
to
. A magician with an assistant perform a trick. The magician leaves the hall and the spectator writes a sequence of
elements on the board from the set
. The magician’s assistant looks at them and adds
more elements from
to the existing sequence. After that the spectator replaces three of these
numbers by random elements of
(it is permitted to change them by themselves, that is to not change anything at all, for example). The magician enters and looks at the resulting row of
numbers and without error names the original
numbers written by the spectator. Find the minimal possible
for which the trick is possible.











