import heapq
N = int(input())
A = list(map(int,input().split()))
A = sorted([(i+1,A[i]) for i in range(N-1)],key=lambda x:x[1])
INFTY = 10**6
dp = [INFTY for _ in range(N+1)]
dp[N] = 0
heap1 = []
heap2 = [(-N,dp[N])]
for j in range(N-2,-1,-1):
    i,r = A[j]
    while heap2:
        if -heap2[0][0]>r:
            heapq.heappop(heap2)
        elif i+1<=-heap2[0][0]<=r:
            k,v = heapq.heappop(heap2)
            k = -k
            heapq.heappush(heap1,(v,k))
        else:break
    while heap1 and heap1[0][1]>r:
        heapq.heappop(heap1)
    dp[i] = dp[i+1]+1
    if heap1:
        dp[i] = min(heap1[0][0]+1,dp[i])
    heapq.heappush(heap2,(-i,dp[i]))
print(dp[1])