#!/bin/python import sys n = int(raw_input().strip()) a = map(int,raw_input().strip().split(' ')) a.sort() unique = set(a) # init count dict count = {} for i in unique: count[i] = 0 for i in a: count[i] += 1 max_integers = 0 for i in unique: integers = count[i] if (i - 1) in unique: integers += count[i-1] if integers > max_integers: max_integers = integers print max_integers