n=int(input())
r=list(map(int,input().split()))
d=[-1]*(n+1)
g=[[] for _ in range(n+1)]
for i in range(n-1):
    for j in range(i+2,r[i]+1):
        g[i+1].append(j)
from collections import deque
q=deque()
q.append(1)
d[1]=0
while q:
    now=q.popleft()
    for to in g[now]:
        if to==n:
            print(d[now]+1)
            exit()
        if d[to]==-1:
            d[to]=d[now]+1
            q.append(to)