import java.io.File;
import java.util.Scanner;

/**
 * https://www.hackerrank.com/contests/101hack44/challenges/picking-numbers
 */
public class PickingNumbers {
    private static final int MAX = 100;
    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);
        //Scanner scanner = new Scanner(new File("pickingNumbers"));
        int n = scanner.nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = scanner.nextInt();
        }
        scanner.close();
        System.out.println(new PickingNumbers(n, a).count());
    }

    int n;
    int[] a;
    public PickingNumbers(int n, int[] a) {
        this.n = n;
        this.a = a;
    }

    private int count() {
        int[] count = new int[MAX];
        for (int i = 0; i < n; i++) {
            count[a[i]]++;
        }

        int maxSize = 0;
        for (int j = 1; j < MAX; j++) {
            int size = count[j-1] + count[j];
            maxSize = Math.max(size, maxSize);
        }
        return maxSize;
    }

}