import java.io.*;
import java.util.*;

public class Mark {

    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);

        int N = sc.nextInt();
        int[] cnts = new int[300];
        for (int i = 0; i < N; ++i) cnts[sc.nextInt()]++;

        int M = 0;
        for (int i = 0; i < 300; ++i) for (; cnts[i] > 0 && 2*M-2-i+1 < cnts[i]; ++M);

        System.out.println(M);
    }

}