from collections import *

N = int(input())
R = list(map(int, input().split()))
G = [[] for i in range(N)]
for i in range(1, N):
    G[i].append((i - 1, 0))
    
for i in range(N-1):
    G[i].append((R[i]-1, 1))
    
Q = deque()
Q.append(0)
inf = 10 ** 18
dist = [inf] * N
dist[0] = 0
while Q:
    u = Q.popleft()
    for v, c in G[u]:
        if dist[v] <= dist[u] + c:
            continue
        dist[v] = dist[u] + c
        if c:
            Q.append(v)
        else:
            Q.appendleft(v)
print(dist[-1])