55. A person worked for 24 consecutive days and earned 1900 yuan. He works full days from Monday to Friday, with a daily wage of 100 yuan; works half days on Saturday, with a wage of 50 yuan; and does not work on Sunday, with no wage. It is known that he started working from a certain day in late March. Given that March 1st is a Sunday, the day he finished working is April $\qquad$th.
Reference answer: 18