# Math

posted by
**Bob**
.

An elevator named L in "63 Building" in Seoul is notorious for its low speed. It takes 3 seconds for L just to move one floor. It takes another 20 seconds for it to have its door open and close automatically.

What is even more frustrating, is that the elevator travels only to odd-numbered floors, and the doors will automatically open and close at all odd numbered floors.

How long will it take (in seconds) for L leaving the 1st floor "just to arrive" at the 35th floor?

Note:

Do not include the time taken for the doors to open / close at the 1st or 35th floor.