author="himanshu malhotra"
aa,bb=500,500
for _ in xrange(1):
    n=input()
    li=map(int,raw_input().split())
    ct=[0 for i in xrange(110)]
    for i in xrange(n):
        ct[li[i]]+=1
    #print ct
    mm=float("-inf")
    for i in xrange(101):
        mm=max(mm,ct[i]+ct[i+1])
    print mm