INF = 10 ** 18
n = int(input())
r = list(map(int,input().split()))
dp = [INF] * (n + 1)
dp[n - 1] = 0

for i in range(n - 2, -1, -1):
    dp[i] = min(dp[i], dp[i + 1] + 1, dp[r[i] - 1] + 1)

print(dp[0])