Time Limit: Java: 5000 ms / Others: 5000 ms
Memory Limit: Java: 32768 KB / Others: 32768 KB
Advanced Cargo Movement, Ltd. uses trucks of different types. Some trucks are used for vegetable delivery, other for furniture, or for bricks. The company has its own code describing each type of a truck. The code is simply a string of exactly seven lowercase letters (each letter on each position has a very special meaning but that is unimportant for this task). At the beginning of company's history, just a single truck type was used but later other types were derived from it, then from the new types another types were derived, and so on.
Today, ACM is rich enough to pay historians to study its history. One thing
historians tried to find out is so called derivation plan -- i.e. how
the truck types were derived. They defined the distance of truck types as the
number of positions with different letters in truck type codes. They also
assumed that each
truck type was derived from exactly one other truck type (except for the first
truck type which was not derived from any other type). The quality of a
derivation plan was then defined as
Since historians failed, you are to write a program to help them. Given the codes of truck types, your program should find the highest possible quality of a derivation plan.