import java.util.Arrays;
import java.util.Scanner;
import java.util.stream.IntStream;

public class A {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
        int[] nn = new int[n];
		IntStream.range(0, n).forEach((int i) -> {
			nn[i] = sc.nextInt();
		});
        Arrays.sort(nn);

        int mlen = 0;
        for (int i = 0; i < nn.length; i++) {
            int s = nn[i];
            int len = 0;
            for (int j = i; j < nn.length && nn[j] - s < 2; j++) {
                ++len;
            }
            mlen = Math.max( mlen, len );
        }
        System.out.println( mlen );
	}
}