n=input()
l=map(int,raw_input().split())
l.sort()
max=0;
p1=0
p2=p1+1
while p2<n:
    while p2<n and l[p2]-l[p1]<=1:
        p2=p2+1
    if p2-p1>max:
        max=p2-p1
    p1=p2
    p2=p2+1
print max