import java.util.Arrays;
import java.util.Scanner;

/**
 * 第一题AC.
 */
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        while (in.hasNext()){
            int n = in.nextInt();
            int[] d = new int[n];
            for (int i = 0; i < n; i++) {
                d[i] = in.nextInt();
            }
            Arrays.sort(d);
            int l = 1, add = 0;
            for(int j=1;j<n;j++){
                if(d[j]-d[j-1]>20){
                    if((j-l)%3!=0){
                        add+=(3-(j-l)%3);
                        l=j;
                    }
                }
            }
            if((n-l+1)%3!=0)
                add+=(3-(n-l+1)%3);
            System.out.println(add);
        }
    }
}