#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;
int cmp(const int &a,const int &b)
{
if (a<b) return 1;
else return 0;
}
int main()
{
int n;
int d[6000000];
int a[6000000];
scanf("%d",&n);
for (int i=1;i<=n;i++)
scanf("%d",&d[i]);
sort(d+1,d+n+1,cmp);
int tot=0;

for (int i=n;i>=1;i--)
{
a[i]=0;
if (a[i+1]==0 && i!=n) goto loop;
a[i]=1;
for (int j=n;j>=i;j--)
if (d[j]-j+1>d[i]) {
a[i]=0;break;}
loop:tot=tot+a[i];
}
printf("%d",tot);
return 0;
}