import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.LongStream;

public class Main {

	public static void main(String[] args) throws IOException {
		new Main().solve();
	}

	private void solve() throws IOException {
		try {
			//				solveA();
			//			solveB();
			//			solveC();
			solveC2();
			//			 solveD();
			//			 solveE();
			//			 solveF();
		} finally {
			if (in != null) {
				in.close();
			}
			if (out != null) {
				out.flush();
				out.close();
			}
		}

	}

	private void solveA() {
		long numX = nextLong();
		long numT = nextLong();

		out.println(numX - numT > 0 ? numX - numT : 0);
	}

	private void solveB() {
		String wk = next();

		StringBuilder builder = IntStream.range(0, wk.length()).filter(i -> (i % 2 == 0))
				.collect(() -> new StringBuilder(), (t, i) -> {
					t.append(wk.charAt(i));
				}, (t, u) -> t.append(u));

		out.println(builder.toString());
	}

	private void solveC2() {
		int numN = nextInt();

		long[] wk = LongStream.range(0, numN).map(i -> nextLong()).toArray();

		Map<Long, Long> wkCount = Arrays.stream(wk).mapToObj(i -> new Long(i))
				.collect(Collectors.groupingBy(s -> s, Collectors.counting()));

		long res = 0;
		for (long j = 0; j <= 100000; j++) {
			long tmp = wkCount.getOrDefault(j, 0l) + wkCount.getOrDefault(j + 1, 0l) + wkCount.getOrDefault(j - 1, 0l);
			res = Long.max(res, tmp);
		}

		out.println(res);
	}

	private void solveC() {
		int numN = nextInt();

		long[] wk = LongStream.range(0, numN).map(i -> nextLong()).toArray();

		Map<Long, Long> wkCount = Arrays.stream(wk).collect(() -> new HashMap<Long, Long>(),
				(t, i) -> {
					long constVal = 1;
					t.merge(i, constVal, (oldV, newV) -> oldV + newV);
					t.merge(i + 1, constVal, (oldV, newV) -> oldV + newV);
					t.merge(i - 1, constVal, (oldV, newV) -> oldV + newV);
				},
				(t, u) -> t.putAll(u));

		Entry<Long, Long> entryWk = null;
		for (Entry<Long, Long> entry : wkCount.entrySet()) {
			if (entryWk == null) {
				entryWk = entry;
			} else {
				if (entryWk.getValue() < entry.getValue()) {
					entryWk = entry;
				}
			}
		}

		out.println(entryWk.getValue());
	}

	private void solveD() {
		int numN = nextInt();

		out.println("");
	}

	private void solveE() {
		int numN = nextInt();

		out.println("");
	}

	private void solveF() {
		int numN = nextInt();

		out.println("");
	}

	private final PrintWriter out = new PrintWriter(System.out);
	private final InputStream in = System.in;
	private final byte[] buffer = new byte[1024];
	private int ptr = 0;
	private int buflen = 0;

	private boolean hasNextByte() {
		if (ptr < buflen) {
			return true;
		} else {
			ptr = 0;
			try {
				buflen = in.read(buffer);
			} catch (IOException e) {
				e.printStackTrace();
			}
			if (buflen <= 0) {
				return false;
			}
		}
		return true;
	}

	private int readByte() {
		if (hasNextByte())
			return buffer[ptr++];
		else
			return -1;
	}

	private static boolean isPrintableChar(int c) {
		return 33 <= c && c <= 126;
	}

	private void skipUnprintable() {
		while (hasNextByte() && !isPrintableChar(buffer[ptr]))
			ptr++;
	}

	public boolean hasNext() {
		skipUnprintable();
		return hasNextByte();
	}

	public int nextInt() {
		return Integer.parseInt(next());
	}

	public String next() {
		if (!hasNext())
			throw new NoSuchElementException();
		StringBuilder sb = new StringBuilder();
		int b = readByte();
		while (isPrintableChar(b)) {
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}

	public long nextLong() {
		if (!hasNext())
			throw new NoSuchElementException();
		long n = 0;
		boolean minus = false;
		int b = readByte();
		if (b == '-') {
			minus = true;
			b = readByte();
		}
		if (b < '0' || '9' < b) {
			throw new NumberFormatException();
		}
		while (true) {
			if ('0' <= b && b <= '9') {
				n *= 10;
				n += b - '0';
			} else if (b == -1 || !isPrintableChar(b)) {
				return minus ? -n : n;
			} else {
				throw new NumberFormatException();
			}
			b = readByte();
		}
	}
}

Measured memory_bytes: 45464