import java.io.*; import java.util.*; import java.text.*; import java.math.*; import java.util.regex.*; public class Solution { public static void main(String[] args) { Scanner in = new Scanner(System.in); int n = in.nextInt(); int[] a = new int[n]; int[] f = new int[102]; for(int a_i=0; a_i < n; a_i++){ a[a_i] = in.nextInt(); f[a[a_i]]++; } int max = 0; for(int i=0;i<=100;i++){ if(f[i]+f[i+1]>max)max=f[i]+f[i+1]; } System.out.println(max); } }