Weather conditions#674
The OlympAirways airline's flight system is designed so that it is possible to travel from any airport served by the airline to any other airport, possibly with several connecting flights. Each flight connects two airports and operates in both directions.
However, sometimes certain flights cannot be operated for a period of time due to bad weather conditions. As a result, a passenger may not be able to travel from airport to airport using only OlympAirways flights. To analyze such scenarios, the company's research department has introduced the concept of the vulnerability number between a pair of airports and . This number is defined as the number of flights whose cancellation (while all other flights operate normally) would make it impossible to travel from airport to airport .
Given information about all flights operated by the airline, write a program to determine the sum of the vulnerability numbers for all pairs of airports.
The first line contains an integer (1 \leq N \leq 100) — the number of airports served by the airline. The second line contains an integer (1 \leq M \leq 4950) — the number of flights operated by the airline. Each of the next lines contains a pair of integers, from to , representing the numbers of the airports connected by a flight.
Print one integer: the sum of the vulnerability numbers between all distinct pairs of airports and such that the number of is less than the number of .
Example 1