Official algorithmic problem description and constraints.
Vlad is planning to hold π rounds next month. Each round should contain one problem of difficulty levels 'A', 'B', 'C', 'D', 'E', 'F', and 'G'.
Vlad already has a bank of π problems, where the π-th problem has a difficulty level of ππ. There may not be enough of these problems, so he may have to come up with a few more problems.
Vlad wants to come up with as few problems as possible, so he asks you to find the minimum number of problems he needs to come up with in order to hold π rounds.
For example, if π=1, π=10, π= 'BGECDCBDED', then he needs to come up with two problems: one of difficulty level 'A' and one of difficulty level 'F'.
Detailed video explanations, mathematical intuition, and clean C++ implementation code.
