Please explain the solution step by step. Thank you.

2. Deadfish problem: Deadfish is a simple programming language that has a single accumu- lator to store data, and four instructions that modify the accumulator. The accumulator always starts with 0. The four instructions that modify the accumulator are: i (incre- ment), d (decrement), s (square), and o (output). The Deadish problem is to find a sequence of instructions that produces a given non-negative number