good sequence

// ********* Assalamualaikum****** IN the name of my Almighty****:):)***
#include<bits/stdc++.h>
using namespace std;
#define suni ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define endl "\n"
#define f(i,a,b) for(int i=a;i<= b;i++)
#define ff(i,a,b) for(int i= a;i>=b;i--)
#define T int t; cin >>t; while(t--)
#define vi  vector<int>
#define vll vector<long long>
#define vs vector<string>
#define vp vector<pair
#define pii pair<int,int>
#define pb push_back
#define mk make_pair
#define b(a) a.begin(),a.end()
#define rb(a) a.rbegin(),a.rend()
#define I  int
#define ll long long
#define st string
#define C char
#define MN int main()
#define fa(u,v) for(auto u:v)

 MN
 {
     I n;
     cin>> n;
     map<I,I>m;
     f(i,1,n) {
         I a;
         cin>>a;
         m[a]++;
     }
     I cnt=0;
     fa(u,m){
         if(u.second>=u.first) cnt+=(u.second-u.first);
         else cnt+=u.second;
     }
     cout<<cnt<<endl;
 }
//*******Happy Coding*******???******