import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }
        Arrays.sort(arr);
        for (int i = 1; i < n; i++) {
            if (arr[i] == arr[i - 1] + 1) {
                System.out.println(2);
                return;
            }
        }
        System.out.println(1);
    }
}