import sys
input = sys.stdin.readline
N = int(input())
a = list(map(int, input().split()))

e = [[] for _ in range(N)]
for x in range(N - 1): e[x + 1].append((x, 0))
for i in range(N - 1): e[i].append((a[i] - 1, 1))

from collections import deque as dq

Q = dq([0])
dp = [N + 1] * N
dp[0] = 0
while len(Q):
  x = Q.popleft()
  for y, c in e[x]:
    if dp[y] > dp[x] + c:
      dp[y] = dp[x] + c
      if c: Q.append(y)
      else: Q.appendleft(y)
print(dp[-1])