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

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);
        int lCount = 1;  
        int currCount = 1;  
        for (int i = 1; i < arr.length; i++) {

            if (arr[i] == arr[i - 1] + 1) {
                currCount++;

                if (currCount > lCount) {
                    lCount = currCount;}
            } else if (arr[i] == arr[i - 1]) {
                continue;
            } else {
                currCount = 1;
            }
        }
        System.out.println("Longest consecutive sequence length: " + lCount);
    }
}