Passage: Despite being badly injured, Alexey managed to return to the Soviet-controlled territory. During his 18-day-long journey his injuries deteriorated so badly that both of his legs had to be amputated below the knee. Desperate to return to his fighter pilot service, he subjected himself to nearly a year of exercise to master the control of his prosthetic devices, and succeeded at that, returning to flying in June 1943.

Question: How many days was his journey?
18