Solution.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

class Result {

  /*
   * Complete the 'pickingNumbers' function below.
   *
   * The function is expected to return an INTEGER.
   * The function accepts INTEGER_ARRAY a as parameter.
   */

  public static int pickingNumbers(List<Integer> a) {
    Collections.sort(a);
    int start = 0;
    int i = 0;
    int max = 0;
    while (i < a.size()) {
      if (Math.abs(a.get(start) - a.get(i)) > 1) {
        start = i;
      }
      max = Math.max(max, i - start + 1);
      i++;
    }
    i--;

    return Math.max(max, i - start + 1);
  }

}

public class Solution {
  public static void main(String[] args) throws IOException {
    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
    BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

    int n = Integer.parseInt(bufferedReader.readLine().trim());

    List<Integer> a = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
        .map(Integer::parseInt)
        .collect(toList());

    int result = Result.pickingNumbers(a);

    bufferedWriter.write(String.valueOf(result));
    bufferedWriter.newLine();

    bufferedReader.close();
    bufferedWriter.close();
  }
}