import sys input = lambda : sys.stdin.readline().rstrip() sys.setrecursionlimit(2*10**5+10) write = lambda x: sys.stdout.write(x+"\n") debug = lambda x: sys.stderr.write(x+"\n") writef = lambda x: print("{:.12f}".format(x)) ### セグメント木(はやい) class SG: def __init__(self, n, v=None): self._n = n self.geta = 0 x = 0 while (1 << x) < n: x += 1 self._log = x self._size = 1 << self._log self._d = [ninf] * (2 * self._size) if v is not None: for i in range(self._n): self._d[self._size + i] = v[i] for i in range(self._size - 1, 0, -1): self._update(i) def _update(self, k): self._d[k] = op(self._d[2 * k], self._d[2 * k + 1]) def update(self, p, x): assert 0 <= p < self._n x -= self.geta p += self._size self._d[p] = x for i in range(1, self._log + 1): # self._update(p >> i) k = p>>i self._d[k] = op(self._d[2 * k], self._d[2 * k + 1]) def get(self, p): # assert 0 <= p < self._n return self._d[p + self._size] + self.geta def check(self): return [self.get(p) for p in range(self._n)] def query(self, left, right): # [l,r)の総和 assert 0 <= left <= right <= self._n sml = ninf smr = ninf left += self._size right += self._size # 外側から計算していく(lは小さい側から, rは大きい側から) while left < right: if left & 1: sml = op(sml, self._d[left]) left += 1 if right & 1: right -= 1 smr = op(self._d[right], smr) left >>= 1 right >>= 1 return op(sml, smr) + self.geta def update_all(self, v): # 全体加算 self.geta += v def query_all(self): return self._d[1] + self.geta def max_right(self, left, f): """f(op(a[l], a[l + 1], ..., a[r - 1])) = true となる最大の r -> rはf(op(a[l:r+1]))がFalseになる最小のr """ # assert 0 <= left <= self._n # assert f(ninf) if left == self._n: return self._n left += self._size sm = ninf first = True while first or (left & -left) != left: first = False while left % 2 == 0: left >>= 1 if not f(op(sm, self._d[left])): while left < self._size: left *= 2 if f(op(sm, self._d[left])): sm = op(sm, self._d[left]) left += 1 return left - self._size sm = op(sm, self._d[left]) left += 1 return self._n def min_left(self, right, f): """f(op(a[l], a[l + 1], ..., a[r - 1])) = true となる最小の l """ # assert 0 <= right <= self._n # assert f(ninf) if right == 0: return 0 right += self._size sm = ninf first = True while first or (right & -right) != right: first = False right -= 1 while right > 1 and right % 2: right >>= 1 if not f(op(self._d[right], sm)): while right < self._size: right = 2 * right + 1 if f(op(self._d[right], sm)): sm = op(self._d[right], sm) right -= 1 return right + 1 - self._size sm = op(self._d[right], sm) return 0 op = max ninf = -10**12 inf = 10**12 n = int(input()) a = list(map(int, input().split())) sg = SG(n+1, [ninf]*(n+1)) a.insert(0,0) aa = list((a[i]-i for i in range(n+1))) index = list(range(n+1)) index.sort(key=lambda i : aa[i]) for i in index: if i==0: sg.update(i, 1) else: sg.update(i, sg.query(0,i) + 1) num = sg.query(0, n+1) ans = n + 1 - num print(ans)