/**
 * Created by distro on 13/12/16.
 */

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Prog1 {
    public static void main(String args[]) throws IOException {
        long t1 = System.currentTimeMillis();
        SolverProg1 ob = new SolverProg1();
        ob.Solve();
        long t2 = System.currentTimeMillis();
        System.err.println("Time = " + (t2 - t1) * 1.0 / 1000 + " seconds");
    }
}

class SolverProg1 {
    BufferedReader br;

    private String readString() throws IOException {
        return br.readLine();
    }

    private int readInt() throws IOException {
        return Integer.parseInt(br.readLine());
    }

    private long readLong() throws IOException {
        return Long.parseLong(br.readLine());
    }

    private double readDouble() throws IOException {
        return Double.parseDouble(br.readLine());
    }

    private int[] readIntSequence() throws IOException {
        String temp[] = br.readLine().trim().split(" ");
        int arrtemp[] = new int[temp.length];
        for (int i = 0; i < temp.length; i++) {
            arrtemp[i] = Integer.parseInt(temp[i]);
        }
        return arrtemp;
    }

    private void setInputRedirect() throws FileNotFoundException {
        String InputBasePath = "Input/";
        String InputFile = "Input" + "Prog1" + ".txt";
        System.setIn(new FileInputStream(InputBasePath + InputFile));
    }

    public void Solve() throws IOException {
        //setInputRedirect();
        br = new BufferedReader(new InputStreamReader(System.in));

        // Solution Goes Here
        int N = readInt();
        int maxval = -1;
        int[] arr = readIntSequence();
        Arrays.sort(arr);
        for (int i = 0; i < N; i++) {
            int num = arr[i];
            int count = 1;
            for (int j = i + 1; j < N; j++) {
                if (Math.abs(arr[j] - num) <= 1) {
                    count++;
                } else {
                    break;
                }
            }
            if (count > maxval) {
                maxval = count;
            }
        }
        System.out.println(maxval);
        // Solution Ends Here
    }
}