import java.io.; import java.util.; import java.util.stream.*;

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) {
    int[] freq = new int[101]; // since 0 <= a[i] <= 100
    for (int num : a) {
        freq[num]++;
    }

    int maxLength = 0;
    for (int i = 1; i < freq.length; i++) {
        maxLength = Math.max(maxLength, freq[i] + freq[i - 1]);
    }

    return maxLength;
}

}

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 = Arrays.stream(bufferedReader.readLine().trim().split(" "))
        .map(Integer::parseInt)
        .collect(Collectors.toList());

    int result = Result.pickingNumbers(a);

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

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

}