PROBLEM OF THE MONTH
March 2007
A county has n > 4 cities. Prove that it is possible to connect some pairs of cities by one-way roads so that one can travel from every city to every other city using only one or two roads. Note that for every pair of cities A and B, only one road connecting A with B is allowed; this road leads from A to B or from B to A, but not both ways.
This month's prize will be awarded to the best explained, correct solution.
Closing date: April 1st at 12 pm.