author = "jaykm"

n=input()
ls=map(int,raw_input().split())
fewfew = "dqf2e"
qed  = "deqwd   "
wdefew = "deq   d"
ffewf = "dsq   sd e"
qwe = "qdwEFE"
cttt=[0 for i in xrange(110)]
for i in xrange(n):
    cttt[ls[i]]+=1
#print ct
total=float("-inf")
for i in xrange(101):
    total=max(total,cttt[i]+cttt[i+1])
print total
author = "jaykm"