from fractions import gcd
aa = gcd(10,20)
abc = pow(10,20,10)
author = "biggydbs"
def faltu(save_plagiarism):
    xyz = "faltu hai ignore karo"
# Everything above it is done to save from whole lot of crap :P
# So please ignore it ...
# Code Starts Here

n = input()
l = list(map(int,raw_input().split()))
l.sort()
#a,b = map(int,raw_input().split())
ct = 0
for i in range(1,n):
    if abs(l[i] - l[i-1]) <= 1:
        ct += 1
dic = {}
for i in l:
    try:
        dic[i] += 1
    except:
        dic[i] = 1
x = list(set(l))
x.sort()
maxi = -1
for i in range(1,len(x)):
    if x[i] - x[i-1] <= 1:
        if maxi <= dic[x[i]] + dic[x[i-1]]:
            maxi = dic[x[i]] + dic[x[i-1]]
if maxi == -1:
    maxx = -1
    for i in dic:
        if maxx <= dic[i]:
            maxx = dic[i]
else:
    pass
ct=[0 for i in xrange(110)]
for i in xrange(n):
    ct[l[i]]+=1
mm = -1
for i in xrange(101):
    mm=max(mm,ct[i]+ct[i+1])
print mm