Question $13$

What is the output?c$0$c$1$ c$2$ bo b$1$ b$2$coc$1$ c$2$b$0$b$1$b$2$ a$0$ a$1$ a$2$c$1$ c$2$ c$3$ b$1$ b$2$ b$3$c$2$c$1$c$0$b$2$b$1$b$0$