output_description: Print the minimum number of elements that needs to be removed so that a will
  be a good sequence.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
      a_1 a_2 ... a_N
attempt: import sys
  import math
  import copy
  import heapq
  from functools import cmp_to_key
  from bisect import bisect_left, bisect_right
  from collections import defaultdict, deque, Counter
  
  sys.setrecursionlimit(1000000)
  
  # input aliases
  input = sys.stdin.readline
  getS = lambda: input().strip()
  getN = lambda: int(input())
  getList = lambda: list(map(int, input().split()))
  getZList = lambda: [int(x) - 1 for x in input().split()]
  
  INF = float("inf")
  MOD = 10**9 + 7
  divide = lambda x: pow(x, MOD - 2, MOD)
  
  
  def nck(n, k, kaijyo):
      return (npk(n, k, kaijyo) * divide(kaijyo[k])) % MOD
  
  
  def npk(n, k, kaijyo):
      if k == 0 or k == n:
          return n % MOD
      return (kaijyo[n] * divide(kaijyo[n - k])) % MOD
  
  
  def fact_and_inv(SIZE):
      inv = [0] * SIZE  # inv[j] = j^{-1} mod MOD
      fac = [0] * SIZE  # fac[j] = j! mod MOD
      finv = [0] * SIZE  # finv[j] = (j!)^{-1} mod MOD
      inv[1] = 1
      fac[0] = fac[1] = 1
      finv[0] = finv[1] = 1
      for i in range(2, SIZE):
          inv[i] = MOD - (MOD // i) * inv[MOD % i] % MOD
          fac[i] = fac[i - 1] * i % MOD
          finv[i] = finv[i - 1] * inv[i] % MOD
  
      return fac, finv
  
  
  class TwoDimGrid:
      # 2次元座標 -> 1次元
      def __init__(self, h, w, wall="#"):
          self.h = h
          self.w = w
          self.size = (h + 2) * (w + 2)
          self.wall = wall
          self.get_grid()
          self.init_cost()
  
      def get_grid(self):
          grid = [self.wall * (self.w + 2)]
          for i in range(self.h):
              grid.append(self.wall + getS() + self.wall)
  
          grid.append(self.wall * (self.w + 2))
          self.grid = grid
  
      def init_cost(self):
          self.cost = [INF] * self.size
  
      def pos(self, x, y):
          return y * (self.w + 2) + x
  
      def getgrid(self, x, y):
          return self.grid[y][x]
  
      def get(self, x, y):
          return self.cost[self.pos(x, y)]
  
      def set(self, x, y, v):
          self.cost[self.pos(x, y)] = v
          return
  
      def show(self):
          for i in range(self.h + 2):
              print(self.cost[(self.w + 2) * i : (self.w + 2) * (i + 1)])
  
      def search(self, s, g):
          grid = self.grid
          move = [(0, 1), (0, -1), (1, 0), (-1, 0)]
          move_eight = [
              (0, 1),
              (0, -1),
              (1, 0),
              (-1, 0),
              (1, 1),
              (1, -1),
              (-1, 1),
              (-1, -1),
          ]
  
  
  def solve():
      n = getN()
      nums = getList()
      c = Counter(nums)
      ans = 0
      for k, v in c.items():
          if v < k:
              ans += v
          elif v > k:
              ans += v - k
      print(ans)
      return
  
  
  def main():
      n = getN()
      for _ in range(n):
          solve()
  
      return
  
  
  if __name__ == "__main__":
      # main()
      solve()
  
problem_description: Statement
  
  You are given a sequence of positive integers of length N, a = (a_1, a_2, ...,
  a_N). Your objective is to remove some of the elements in a so that a will be
  a **good sequence**.
  
  Here, an sequence b is a **good sequence** when the following condition holds
  true:
  
    * For each element x in b, the value x occurs exactly x times in b.
  
  For example, (3, 3, 3), (4, 2, 4, 1, 4, 2, 4) and () (an empty sequence) are
  good sequences, while (3, 3, 3, 3) and (2, 4, 1, 4, 2) are not.
  
  Find the minimum number of elements that needs to be removed so that a will be
  a good sequence.
samples: [{"input": "4\n    3 3 3 3", "output": "1\n    \n\nWe can, for example, remove one occurrence of 3. Then, (3, 3, 3) is a good\nsequence.\n\n* * *"}, {"input": "5\n    2 4 1 4 2", "output": "2\n    \n\nWe can, for example, remove two occurrences of 4. Then, (2, 1, 2) is a good\nsequence.\n\n* * *"}, {"input": "6\n    1 2 2 3 3 3", "output": "0\n    \n\n* * *"}, {"input": "1\n    1000000000", "output": "1\n    \n\nRemove one occurrence of 10^9. Then, () is a good sequence.\n\n* * *"}, {"input": "8\n    2 7 1 8 2 8 1 8", "output": "5"}]