Statement

In another planet, totally different and not at all related to Earth, there is a sneaky epidemic that is infecting most of the population. The symptoms are not always evident, therefore it's spreading pretty much unnoticed. People are arranged in a grid of N rows and M columns. This virus is very infectious, if a person is infected at time t, then at time t+1 all 4 neighbours will be infected as well. Furthermore, the older the person infected, the worse are the effects of the illness! You know the age A_ij of each person. The infection starts at time 0 from a person in the grid, and it evolves until it is noticed. The virus gets noticed when a person on the border is infected; at that point, Mr Withyou, the President of the World, declares a global lockdown, stopping the spreading of the virus...