In the town of Pirates, Captain Jack is the best pirate. Captain Smith is jealous of Jack's popularity. So he challenged Jack to solve the following puzzle:
Given an array A, find the length of the largest contiguous sub-array such that the difference between any two consecutive elements in the sub-array is 1. Captain Jack is a little confused, so he called you, a programmer, for solving this puzzle.

INPUT

First line of input contains a number N i.e. the number of elements in array A. The next line contains N space separated integers representing elements of array.

OUTPUT

Print the largest length of contiguous sub-array satisfying the above given property.

CONSTRAINTS

1 ≤ N ≤ 100000     
0 ≤ A[ i ] ≤ 100000 

SAMPLE INPUT
6
1 3 5 7 8 9

SAMPLE OUTPUT
3
'''
# Read input from stdin and provide input before running code

name = raw_input('What is your name?\n')
print 'Hi, %s.' % name
'''
n=int(raw_input())
a=raw_input()
a=map(int,a.split(' '))
c=0
ma=0
for i in range(0,len(a)-1):
	if abs(a[i]-a[i+1]) == 1:
		c+=1
		if c>ma:
			ma=c
	else:
		c=0
		
	
print ma+1