Each jump is carried out four times in a cycle,

Both quadrilateral ABP4P3 and quadrilateral ABP3P2 are isosceles trapezoid.

Jump 15 times to P4,

A is the extension line from AM⊥P4P 1 to m, from P 1M=4-3= 1,

AP 1=6,∴AM=√35，

P4M=6+ 1=7，

∴ap4&； sup2=35+49=84,

AP4=2√2 1。