/*
    なるべく諦めない！
    なせば大抵なんとかなる！
*/

#define VERNIY st();int ver=0,niy=0,hbk=0

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>
#include <time.h>
#include <limits.h>
#include <float.h>
#include <iostream>
#include <algorithm>
#include <string>
#include <iterator>
#include <vector>
#include <map>
#include <queue>
#include <utility>
#include <functional>
#include <set>
#define LLU unsigned long long int
#define LL long long int
using namespace std;
#define Lfmax DBL_MAX
#define LLUmax ULLONG_MAX
#define LLmax LLONG_MAX
#define dmax INT_MAX
#define vd vector<int>
#define vpd vector<pair<int,int>>
#define vLL vector<long long int>
#define vpLL vector<pair<long long int,long long int>>
#define vLLU vector<unsigned long long int>
#define vpLLU vector<pair<unsigned long long int,unsigned long long int>>
#define pd pair<int,int>
#define pLL pair<long long int,long long int>
#define pLLU pair<unsigned long long int,unsigned long long int>
#define qd queue<int>
#define qpd queue<pair<int,int>>
#define maxpqd priority_queue<int>
#define minpqd priority_queue<int, vector<int>, greater<int>>
#define fr front
#define pb push_back
#define mp make_pair
#define fi first
#define sec second
#define debugarr(a,b) for(int i=0 ; i<b ; i++)printf("%d ",a[i]);printf("\n")
#define newline printf("\n")
#define forin(a,b,c) for(int a=b ; a<c ; ++a)
#define forineq(a,b,c) for(int a=b ; a<=c ; ++a)
#define forde(a,b,c) for(int a=b ; a>=c ; --a)
#define UPC(oo) (oo>='A' && oo<='Z')
#define LWC(oo) (oo>='a' && oo<='z')
#define DGT(oo) (oo>='0' && oo<='9')
#define UPCVOC(oo) (oo=='A' || oo=='E' || oo=='I' || oo=='U' || oo=='O')
#define LWCVOC(oo) (oo=='a' || oo=='e' || oo=='i' || oo=='u' || oo=='o')
#define filein freopen("in.txt","r",stdin);
#define fileout freopen("out.txt","w",stdout);

inline void scd(int &a){scanf("%d",&a);}
inline void scdd(int &a,int &b){scanf("%d %d",&a,&b);}
inline void sctd(int &a,int &b,int &c){scanf("%d %d %d",&a,&b,&c);}
inline void sctlld(LL &a,LL &b,LL &c){scanf("%I64d %I64d %I64d",&a,&b,&c);}
inline void scdlld(LL &a,LL &b){scanf("%I64d %I64d",&a,&b);}
inline void sclld(LL &a){scanf("%I64d",&a);}
inline void scllu(LLU &a){scanf("%I64u",&a);}
inline void scdllu(LLU &a,LLU &b){scanf("%I64u %I64u",&a,&b);}
inline void sctllu(LLU &a,LLU &b,LLU &c){scanf("%I64u %I64u %I64u",&a,&b,&c);}

template<class Ver>
inline void prd(Ver a){cout<<a<<"\n";};
template<class Ver>
inline void prdd(Ver a,Ver b){cout<<a<<" "<<b<<"\n";};
template<class Ver>
inline void prtd(Ver a, Ver b, Ver c){cout<<a<<" "<<b<<" "<<c<<"\n";};

inline void debug(){printf("asd\n");}
template<class Ver>
inline void debugd(Ver a){cout<<"--- "<<a<<endl;};
template<class Ver>
inline void debugdd(Ver a,Ver b){cout<<"--- "<<a<<" "<<b<<endl;};
template<class Ver>
inline void debugtd(Ver a,Ver b,Ver c){cout<<"--- "<<a<<" "<<b<<" "<<c<<endl;};

#define grav 9.8
#define pi 3.14159265

void st()
{
	ios_base::sync_with_stdio(0);
	cin.tie(0);
}

int main()
{
	VERNIY;
	map<LL,LL> a;
	scd(ver);
	forin(i,0,ver)
	{
		scd(niy);
		++a[niy];
	}
	int ans=0;
	for(auto i=a.begin() ; i!=a.end() ; ++i)
	{
		if(i->second<i->first)
		{
			ans+=i->second;
		}
		else if(i->second>i->first)
		{
			ans+=(i->second-i->first);
		}
	}
	if(ans>ver)
	{
		ans=ver;
	}
	prd(ans);

	return 0;
}

/*
    なるべく諦めない！
    なせば大抵なんとかなる！
*/


Measured memory_bytes: 6272