An irresponsible student who skips school on any day with probability 1/5, independent of any other day, has just started attending a certain high school. This high school has a policy that, once a student is absent 4 times, that student is put on probation. What is the expected number of days it takes until the student is put on probation? (Please enter your answer as a decimal, correct to three places.)

please answer it as soon as possible.