import bisect import copy import decimal import fractions import heapq import itertools import math import random import sys import time from collections import Counter,deque,defaultdict from functools import lru_cache,reduce from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max def _heappush_max(heap,item): heap.append(item) heapq._siftdown_max(heap, 0, len(heap)-1) def _heappushpop_max(heap, item): if heap and item < heap[0]: item, heap[0] = heap[0], item heapq._siftup_max(heap, 0) return item from math import gcd as GCD read=sys.stdin.read readline=sys.stdin.readline readlines=sys.stdin.readlines def LIS(lst,weakly=False,inf=float('inf'),restoration=False): f=bisect.bisect_right if weakly else bisect.bisect_left N=len(lst) update=[None]*N dp=[inf]*N for k,x in enumerate(lst): i=f(dp,x) dp[i]=x update[k]=(i,dp[i]) len_lis=bisect.bisect_left(dp,inf) if restoration: lis=[None]*len_lis len_lis-=1 for i,x in update[::-1]: if i==len_lis: lis[len_lis]=x len_lis-=1 return lis else: return len_lis N=int(readline()) A=list(map(int,readline().split())) for i in range(N): A[i]-=i ans=N-LIS(A,weakly=True) print(ans)