from collections import deque

INF = 10 ** 9

N = int(input())

G = [[] for i in range(N)]

R = list(map(int, input().split()))
for i in range(N - 1):
    G[i] += [(R[i] - 1, 1)]
for i in range(N - 1):
    G[i + 1] += [(i, 0)]

dist = [INF] * N
dist[0] = 0
que = deque([0])

while que:
    v = que.popleft()
    for e in G[v]:
        if dist[e[0]] > dist[v] + e[1]:
            dist[e[0]] = dist[v] + e[1]
            if e[1] == 1:
                que.append(e[0])
            else:
                que.appendleft(e[0])

print(dist[N - 1])