#!/bin/python

import sys


n = int(raw_input().strip())
ns = map(int,raw_input().strip().split(' '))
ns.sort()
ns = [0] + [ns[i]-ns[i-1] for i in range(1,n)]
md = 1
dist = 0
for i in range(n):
    dist = 0
    for j in range(i+1,n):
        dist += ns[j]
        if dist > 1:
            break
        else:
            md = max(md,j-i+1)
print md