Roads and Flights

The country of Cheflandia has $N$ cities, with $M$ **one-directional** roads connecting pairs of them. There are also flights between certain pairs of cities. In particular, there's a flight from city $u$ to city $v$ if and only if: - There exists a way to travel from city $u$ to city $v$ via some sequence of roads; **and** - There exists a way to travel from city $v$ to city $u$ via some sequen