Problem - Flight Routes Check (CSES 1682)

Problem: you are given a directed graph representing flight routes between cities. Check if you can travel from any city to any other city (following directed edges). If not possible, print two cities $a$ and $b$ such that you cannot travel from $a$ to $b$.

The graph is strongly connected if and only if it has exactly one SCC. If there are multiple SCCs, pick two nodes in different components to show impossibility.