Ducks have started mysteriously appearing in your room. All ducks make the same sound: "quack". Each duck makes the sound one or more times, one after another. For example, valid sounds for a single duck are "quack", "quackquackquackquack", "quackquack" ...
Recently you learned about substitution ciphers. This problem is about such a cipher. All strings in this problem (both encrypted and decrypted ones) will consist of only uppercase English letters ('A'-'Z').
When encrypting text using a substitution cipher ...
Limak is an old brown bear who likes to play darts.
Limak just picked up an empty scorecard. He then threw a sequence of darts into a dartboard and for each dart he recorded the point value of the ...
You are a traveling salesman. You have already heard a lot about how hard the problems of a traveling salesman can be. Luckily, the one you currently have seems easier.
There are M cities where you can sell products ...
John is standing at the origin of an infinite two-dimensional grid. He is going to move along this grid. During each second he can either stay where he is or he can move by one unit in one of ...