#!/bin/python3

import sys

n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
a = sorted(a)

l=0
ans=0
sz = int( len(a) )
i = 1 
#print(a)
while( i < sz):
    if( abs(a[i] - a[l]) < 2 ):
        ans = max(ans,i - l +1)
        #print('*',i,l, a[i], a[l],ans)
        i+=1
    else:
        #print(i,l, a[i], a[l],ans)
        l+=1
print(ans)