/*
TASK:edi
LANG:C++
*/
//exod40:)
#include <cstdio>
#include <algorithm>
using namespace std;

#define MAXN 131072

int cmp(int a,int b)
{
    return a>b;
}

int a[MAXN];
int n;

int solve()
{
    int cnt;
    int i,j;
    int b;
    
    cnt=0;
    
    for (i=0;i<n;i++)
    {
        cnt++;
        
        if (i==n-1)
        {
            b=0;
        }
        else
        {
            b=a[i+1];
        }
        
        for (j=a[i];j>b;j--)
        {
            if (j<=cnt)
            {
                return j;
            }
        }
    }
}

int main()
{
    int i,j;
    
    scanf ("%d",&n);
    
    for (i=0;i<n;i++)
    {
        scanf ("%d",&a[i]);
    }
    
    sort (&a[0],&a[n],cmp);
    
   // printf ("%d\n",solve());
    
}
