Fox Ciel has n boxes in her room. They have the same size and weight, but they might have different strength. The i-th box can hold at most xi boxes on its top (we'll call xi the strength of the box). 

Since all the boxes have the same size, Ciel cannot put more than one box directly on the top of some box. For example, imagine Ciel has three boxes: the first has strength 2, the second has strength 1 and the third has strength 1. She cannot put the second and the third box simultaneously directly on the top of the first one. But she can put the second box directly on the top of the first one, and then the third box directly on the top of the second one. We will call such a construction of boxes a pile.

<image>

Fox Ciel wants to construct piles from all the boxes. Each pile will contain some boxes from top to bottom, and there cannot be more than xi boxes on the top of i-th box. What is the minimal number of piles she needs to construct?

Input

The first line contains an integer n (1 ≤ n ≤ 100). The next line contains n integers x1, x2, ..., xn (0 ≤ xi ≤ 100).

Output

Output a single integer — the minimal possible number of piles.

Examples

Input

3
0 0 10


Output

2


Input

5
0 1 2 3 4


Output

1


Input

4
0 0 0 0


Output

4


Input

9
0 1 0 2 0 1 1 2 10


Output

3

Note

In example 1, one optimal way is to build 2 piles: the first pile contains boxes 1 and 3 (from top to bottom), the second pile contains only box 2.

<image>

In example 2, we can build only 1 pile that contains boxes 1, 2, 3, 4, 5 (from top to bottom).

<image>
import java.util.*;
import java.math.*;
import java.io.*; 
 public class B{
static int[] dx={-1,1,0,0};
static int[] dy={0,0,1,-1};
    static FastReader scan=new FastReader();
   public static PrintWriter out = new PrintWriter (new BufferedOutputStream(System.out));
  static ArrayList<Pair>es;
  static LinkedList<Integer>edges[];
   static boolean prime[];
   static void sieve(int n) 
    { 
        
        prime = new boolean[n+1]; 
        for(int i=0;i<n;i++) 
            prime[i] = true; 
          
        for(int p = 2; p*p <=n; p++) 
        { 
           
            if(prime[p] == true) 
            { 
                
                for(int i = p*p; i <= n; i += p) 
                    prime[i] = false; 
            } 
        } 
          
        
    }      
     public static int lowerBound(long[] array, int length, long value) {
        int low = 0;
        int high = length;
        while (low < high) {
            final int mid = (low + high) / 2;
            //checks if the value is less than middle element of the array
            if (value <= array[mid]) {
                high = mid;
            } else {
                low = mid + 1;
            }
        }
        return low;
    }
    public static int upperBound(long[] array, int length, long value) {
        int low = 0;
        int high = length;
        while (low < high) {
            final int mid = low+(high-low) / 2;
            if ( array[mid]>value) {
                high = mid ;
            } else {
                low = mid+1;
            }
        }
        return low;
    }
static long mod(long x,long y)
    {
        if(x<0)
            x=x+(-x/y+1)*y;
        return x%y;
    }    
     static boolean isPowerOfTwo(long n) 
    { 
        if (n == 0) 
            return false; 
  
        while (n != 1) { 
            if (n % 2 != 0) 
                return false; 
            n = n / 2; 
        } 
        return true; 
    } 

  
   
static boolean isprime(long x)
           {
            for(long i=2;i*i<=x;i++)
                if(x%i==0)
                    return false;
                return true;
           }


static int dist(int x1,int y1,int x2,int y2){
return Math.abs(x1-x2)+Math.abs(y1-y2);
}


    static long cuberoot(long x)
    {
        long lo = 0, hi = 1000005;
        while(lo<hi)
        {
            long m = (lo+hi+1)/2;
            if(m*m*m>x)
                hi = m-1;
            else
                lo = m;
        }
        return lo;
    }
     public static int log2(int N) 
    { 
  
        // calculate log2 N indirectly 
        // using log() method 
        int result = (int)(Math.log(N) / Math.log(2)); 
  
        return result; 
    } 
  
    
   
       static long gcd(long a, long b) {
    if(a!=0&&b!=0)
        while((a%=b)!=0&&(b%=a)!=0);
    return a^b;
}
    static long LCM(long a,long b){
    return (Math.abs(a*b))/gcd(a,b);
   }
   public static class comp1 implements Comparator<Pair>{  
public int compare(Pair o1,Pair o2){
   if(o2.x==o1.x)
    return (o2.y-o1.y)>0?1:-1;
return (o2.x-o1.x)>0?1:-1;
}
  }
     public static class comp2 implements Comparator<Pair>{  
public int compare(Pair o1,Pair o2){
 
return (o2.ab-o1.ab)>0?1:-1;
}
  }
 static boolean can(int m,int s)
 {
    return (s>=0&&s<=m*9);
 }
   static boolean collinear(long x1, long y1, long x2,  
                          long y2, long x3, long y3) 
{
    long a = x1 * (y2 - y3) +  
                x2 * (y3 - y1) +  
                x3 * (y1 - y2); 
                if(a==0)
                    return true;
                return false;
}

static int n;
static int arr[];
static int dp[][];


static int rec(int i,int last)
{
    if(i==n)
        return 0;
    if(dp[i][last]!=-1)
        return dp[i][last];
    int max=Integer.MAX_VALUE;
    if(arr[i]==0)
    {
         max=1+rec(i+1,0);
    }
    else if(arr[i]==1)
    {
  
        if(last==1)
            max=1+rec(i+1,0);
        else 
        {
            max=Math.min(rec(i+1,0)+1,rec(i+1,1));
        }
    }
    else if(arr[i]==2)
    {
        if(last==2)
        {
            max=1+rec(i+1,0);
        }
        else 
            max=Math.min(rec(i+1,0)+1,rec(i+1,2));
    }
    else 
    {
        if(last==1)
            max=Math.min(rec(i+1,0)+1,rec(i+1,2));
        else if(last==2)
            max=Math.min(rec(i+1,0)+1,rec(i+1,1));
        else 
        max=Math.min(rec(i+1,1),Math.min(rec(i+1,2),rec(i+1,0)+1));
    }
    return dp[i][last]=max;
} 

public static void main(String[] args)  throws Exception 
{
//java.util.Scanner scan=new java.util.Scanner(new File("mootube.in"));
 //PrintWriter out = new PrintWriter (new FileWriter("mootube.out"));
//scan=new FastReader("equal.in");
//out = new PrintWriter ("output.txt");
//System.out.println(3^2);
//System.out.println(19%4);
   //StringBuilder news=new StringBuilder("ab");
   //news.deleteCharAt(1);
   //news.insert(0,'c');
   //news.deleteCharAt(0);
   //System.out.println(news);
   //System.out.println(can(2,15));
    //System.out.println(LCM(2,2));
   // System.out.println(3^2);
int tt=1;
//tt=scan.nextInt();


  outer:while(tt-->0)
 {
int n=scan.nextInt();
 int arr[]=new int[n];
 for(int i=0;i<n;i++)
 {
    arr[i]=scan.nextInt();
 }
 Arrays.sort(arr);
 int count[]=new int[n];
 for(int l:arr)
 {
    for(int i=0;i<n;i++)
    {
        if(count[i]<=l)
        {
            count[i]++;
            break;
        }
    }
 }
 int res=0;
 for(int i=0;i<n;i++)
    if(count[i]!=0)
        res++;
    out.println(res);





}
out.close();
}    



static long binexp(long a,long n,long mod)
{
    if(n==0)
       return 1;
    long res=binexp(a,n/2,mod)%mod;
    res=res*res;
    if(n%2==1)
        return (res*a)%mod;
    else 
        return res%mod;
}
static class special implements Comparable<special> {
    char x;
    int id;
    special(char x,int id)
    {
        this.id=id;
       this.x=x;
    }
    public int compareTo(special o)
    {
        return o.id-id;
    }
   
}
 public static  long pow(long b, long e) {
            long r = 1;
            while (e > 0) {
                if (e % 2 == 1) r = r * b ;
                b = b * b;
                e >>= 1;
            }
            return r;
        }

private static void sort(int[] arr) {
        List<Integer> list = new ArrayList<>();
        for (int object : arr) list.add(object);
        Collections.sort(list);
        for (int i = 0; i < list.size(); ++i) arr[i] = list.get(i);
    }
 public static class FastReader {
        BufferedReader br;
        StringTokenizer root;
        
 
        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        FastReader(String filename)throws Exception
        {

            br=new BufferedReader(new FileReader(filename));
        }
 
        String next() {
            while (root == null || !root.hasMoreTokens()) {
                try {
                    root = new StringTokenizer(br.readLine());
                } catch (Exception addd) {
                    addd.printStackTrace();
                }
            }
            return root.nextToken();
        }
 
        int nextInt() {
            return Integer.parseInt(next());
        }
 
        double nextDouble() {
            return Double.parseDouble(next());
        }
 
        long nextLong() {
            return Long.parseLong(next());
        }
 
        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (Exception addd) {
                addd.printStackTrace();
            }
            return str;
        }
         public int[] nextIntArray(int arraySize) {
            int array[] = new int[arraySize];
 
            for (int i = 0; i < arraySize; i++) {
                array[i] = nextInt();
            }
 
            return array;
        }
}
public static class Pair implements Comparable<Pair>{
         int x;
         int y;
         long ab;
        
        int z;
        public Pair(){}
        public Pair(int x1, int y1,int z) {
            x=x1;
            y=y1;
            this.z=z;
        }
        public Pair(int x1, int y1) {
            x=x1;
            y=y1;
            this.ab=x+y;
        
        }
        @Override
        public int hashCode() {
            return (int)(x + 31 * y);
        }
        public String toString() {
            return x + " " + y;
        }
        @Override
        public boolean equals(Object o){
            if (o == this) return true;
            if (o.getClass() != getClass()) return false;
            Pair t = (Pair)o;
            return t.x == x && t.y == y;
        }
        public  int compareTo(Pair o)
        {
            return o.y-y;    
        }
}

}







