Eolymp 325: Dangerous route

Problem statement In one country there are n cities, some of which are connected by two-way routes. Cities are numbered by integers from 1 to n. In times of financial crisis the level of the crime in a state rose and the crime groups are organized. The most dangerous of these was “Timur and his gang” led by a notorious criminal circles by Timur, that commit robberies on most of the roads. As a result, some roads became dangerous to drive.