#include<cstdio>

 #include<algorithm>

 using namespace std;

 int n,a[],f[],g[];

 //f[i]表示前i个人分组合法的组数最大值

 //f[i]=max{f[j]}(0<=j<=i-a[i])+1

 //g[i]=max{g[j]}(0<=j<=i)

 int main()

 {

     int i;

     scanf("%d",&n);

     for(i=;i<=n;i++)    scanf("%d",&a[i]);

     sort(a+,a+n+);

     for(i=;i<=n;i++)

     {

         f[i]=g[max(,i-a[i])]+;

         g[i]=max(g[i-],f[i]);

     }

     printf("%d",f[n]);

     return ;

 }