import sys

n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
ans_list=[]
for i in range(n):
    m = a.count(a[i])
    n = a.count((a[i] + 1))
    o = a.count((a[i] - 1))
    ans = max(m+n, m+o)
    ans_list.append(ans)

print max(ans_list)