Statement

The police is still searching fearsome William! Given the skills of the criminal, who is apparently able to drive his car and find his way through the M roads of the city, the police has placed bombs in some of those roads to stop and eventually catch him. A button pressed at time T will trigger the simultaneous explosion of all the bombs, effectively making some roads unusable. Labelling the N intersections with integers, William is now at the intersection 0 and wants to reach his nest at the intersection N-1. Thanks to his network of fellow criminals, he has come into possession of the plan of the police, knowing for each road from intersection A_i to B_i whether it will explode or not. William knows how many seconds it will cost him to drive through each road, but obviously cannot drive on roads that are already exploded or will explode while driving on them. Is he going to be able to reach his nest and get away with it? If so, how many seconds is it going to take?