import sys, re

from collections import deque, defaultdict, Counter

from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians#, log2

from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby

from operator import itemgetter, mul

from copy import deepcopy, copy

from string import ascii_lowercase, ascii_uppercase, digits

from bisect import bisect, bisect_left, insort, insort_left

from fractions import gcd

from heapq import heappush, heappop

from functools import reduce

def input(): return sys.stdin.readline().strip()

def INT(): return int(eval(input()))

def MAP(): return list(map(int, input().split()))

def LIST(): return list(map(int, input().split()))

def ZIP(n): return list(zip(*(MAP() for _ in range(n))))

sys.setrecursionlimit(10 ** 9)

INF = float('inf')

mod = 10 ** 9 + 7

import numpy as np



N = INT()

a = np.array(LIST())

a = np.bincount(a)

b = a.copy()

b[1:] += a[:-1]

b[:-1] += a[1:]

print((b.max()))



import sys, re

from collections import deque, defaultdict, Counter

from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians#, log2

from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby

from operator import itemgetter, mul

from copy import deepcopy, copy

from string import ascii_lowercase, ascii_uppercase, digits

from bisect import bisect, bisect_left, insort, insort_left

from fractions import gcd

from heapq import heappush, heappop

from functools import reduce

def input(): return sys.stdin.readline().strip()

def INT(): return int(eval(input()))

def MAP(): return list(map(int, input().split()))

def LIST(): return list(map(int, input().split()))

def ZIP(n): return list(zip(*(MAP() for _ in range(n))))

sys.setrecursionlimit(10 ** 9)

INF = float('inf')

mod = 10 ** 9 + 7

#import numpy as np

#from decimal import *



N = INT()

a = LIST()



lim = 10**5+3

cnt = [0]*lim



for n in a:

	cnt[n] += 1



ans = 0

for i in range(2, lim):

	ans = max(ans, cnt[i-2]+cnt[i-1]+cnt[i])

print(ans)
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians  # , log2
from itertools import (
    accumulate,
    permutations,
    combinations,
    combinations_with_replacement,
    product,
    groupby,
)
from operator import itemgetter, mul
from copy import deepcopy, copy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce


def input():
    return sys.stdin.readline().strip()


def INT():
    return int(eval(input()))


def MAP():
    return list(map(int, input().split()))


def LIST():
    return list(map(int, input().split()))


def ZIP(n):
    return list(zip(*(MAP() for _ in range(n))))


sys.setrecursionlimit(10**9)
INF = float("inf")
mod = 10**9 + 7
import numpy as np

N = INT()
a = np.array(LIST())
a = np.bincount(a)
b = a.copy()
b[1:] += a[:-1]
b[:-1] += a[1:]
print((b.max()))

import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians  # , log2
from itertools import (
    accumulate,
    permutations,
    combinations,
    combinations_with_replacement,
    product,
    groupby,
)
from operator import itemgetter, mul
from copy import deepcopy, copy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce


def input():
    return sys.stdin.readline().strip()


def INT():
    return int(eval(input()))


def MAP():
    return list(map(int, input().split()))


def LIST():
    return list(map(int, input().split()))


def ZIP(n):
    return list(zip(*(MAP() for _ in range(n))))


sys.setrecursionlimit(10**9)
INF = float("inf")
mod = 10**9 + 7
# import numpy as np
# from decimal import *
N = INT()
a = LIST()
lim = 10**5 + 3
cnt = [0] * lim
for n in a:
    cnt[n] += 1
ans = 0
for i in range(2, lim):
    ans = max(ans, cnt[i - 2] + cnt[i - 1] + cnt[i])
print(ans)

-import numpy as np - +# import numpy as np +# from decimal import * -a = np.array(LIST()) -a = np.bincount(a) -b = a.copy() -b[1:] += a[:-1] -b[:-1] += a[1:] -print((b.max())) +a = LIST() +lim = 10**5 + 3 +cnt = [0] * lim +for n in a: +    cnt[n] += 1 +ans = 0 +for i in range(2, lim): +    ans = max(ans, cnt[i - 2] + cnt[i - 1] + cnt[i]) +print(ans)