1994 OIM Problems/Problem 3
Problem
In each square of an 
board there is a lamp. When a lamp is touched, it and all the lamps located in the row and column where that lamp belongs change state (those that are on turn off and those that are off turn on). Initially all are turned off. Demonstrate that it is always possible, with an adequate succession of touches, for the entire board to remain lit and find, as a function of 
, the minimum number of touches for all the lamps to light up.
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com
Solution
This problem needs a solution. If you have a solution for it, please help us out by adding it.
