Strolling Cows

Before going to the barn for dinner, the cows like to stroll the N (1 ≤ N ≤ 30,000) pastures while watching the sun set. Each pasture leads to precisely one pasture, though some pastures have more than one pasture emptying into them. For a valid strolling experience, the cows can start in any pasture and must finish in that same pasture without visiting any other pasture twice. Given a description of the pasture paths, deduce the longest possible valid stroll the cows can take.

• Line 1: One integer: N
• Lines 2..N+1: Line M tells the pasture number that pasture M-1 connects to (so line 2 tells which pasture is accessible from pasture 1, etc.)

A single line with the integer that is the largest number of pastures that can be visited on a legal stroll.