n=int(raw_input())
l=map(int,raw_input().split())

l.sort()
count_=0
for i in range(len(l)):
    j=i+1
    c=1
    while j<len(l):
        if l[j]<=l[i]+1:
            c+=1
        else:
            break
        j+=1
    count_=max(c,count_)

print count_