import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

public class Solution implements Runnable {

    private void solve() throws IOException {

        int[] cnt = new int[101];
        int N = nextInt();
        for(int i = 0; i < N; ++i) {
            cnt[nextInt()]++;
        }

        int best = 0;
        for(int i = 0; i < 100; ++i) {
            best = Math.max(best,cnt[i] + cnt[i+1]);
        }
        writer.println(best);
    }

    public static void main(String[] args) {
        new Solution().run();
    }

    BufferedReader reader;
    //    BufferedReader reader2;
    StringTokenizer tokenizer;
    PrintWriter writer;
    //    BufferedWriter writer;

    public void run() {
        try {
            reader = new BufferedReader(new InputStreamReader(System.in));
//            reader = new BufferedReader(new FileReader("trees.in"));
            //            reader2 = new BufferedReader(new FileReader("1.in"));
            tokenizer = null;
            writer = new PrintWriter(System.out);
//            writer = new     PrintWriter("trees.out");
//                                                    writer = new BufferedWriter(System.out);
            //                        writer = new BufferedWriter(new OutputStreamWriter(System.out));
            solve();
            reader.close();
            //            reader2.close();
            writer.close();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }

    long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }

    short nextShort() throws IOException {
        return Short.parseShort(nextToken());
    }

    String nextToken() throws IOException {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            tokenizer = new StringTokenizer(reader.readLine());
        }

        return tokenizer.nextToken();
    }

}