from collections import deque

INF = 1 << 60

n = int(input())
r = list(map(int, input().split()))
g = [[] for _ in range(n)]
for u in range(n - 1):
  g[u].append(r[u] - 1)

src = 0
dist = [INF for _ in range(n)]
dist[src] = 0
dq = deque()
dq.append(src)
while len(dq) > 0:
  cur = dq.popleft()
  if cur > 0 and dist[cur - 1] > dist[cur]:
    dist[cur - 1] = dist[cur]
    dq.appendleft(cur - 1)
  for nxt in g[cur]:
    if dist[nxt] > dist[cur] + 1:
      dist[nxt] = dist[cur] + 1
      dq.append(nxt)

print(dist[-1])