38th Polish Mathematical Olympiad Problems 1987

38th Polish Mathematical Olympiad Problems 1987A1.  There are n ≥ 2 points in a square side 1. Show that one can label the points P1, P2, ... , Pn such that ∑i=1n |Pi-1 - Pi|2 ≤ 4, where we use cyclic subscripts, so that P0 means Pn.