Bear and Digit Virus

There are 10 types of viruses — one type with strength 0, one type with strength 1, and so on, up to the last type with strength 9. Limak examines the behavior of a row of N viruses, indexed 1 through N. The initial situation is represented by a string S that consists of N digits, denoting the strengths of the viruses. Stronger viruses will slowly defeat the weaker ones and convert them into the