#!/bin/python3

import sys
import itertools

n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]

def matches(l):
    return all([abs(x[0] - x[1]) <= 1 for x in itertools.combinations(l, 2)])

results = []
def check_list(l):
    if len(l) == 0:
        return
    m = max(l)
    test = [x for x in l if abs(x-m) <= 1]
    # print(test)
    results.append(len(test))
    check_list(list(filter(lambda x: x != m, l)))
    
check_list(a)
print(max(results))