#include <bits/stdc++.h>
#define MOD 1000000007
#define Tran_Hoan_Thien ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define fi first
#define se second
#define pb push_back
#define vi vector<int>
#define ll long long
#define vll vector<ll>
#define db double
using namespace std;
int main(){
    freopen("CAU3.INP ","r",stdin);
    freopen("CAU3.OUT","w",stdout);
    Tran_Hoan_Thien;
    int n;cin>>n;
    vector<int> a(n);
    for(int &x:a) cin>>x;
    sort(a.begin(),a.end(),greater<int> ());
    int dem=1;
    int k=a[0];
    for(int i=1;i<n;i++){
        if(k<=0) break;
        dem++;
        k=min(k-1,a[i]);
    }
    cout<<dem;
    return 0;  
}
 

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