Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length N, a_1,a_2,...,a_N.

For each 1≤i≤N, you have three choices: add 1 to a_i, subtract 1 from a_i or do nothing.

After these operations, you select an integer X and count the number of i such that a_i=X.

Maximize this count by making optimal choices.

Constraints

1≤N≤10^5

0≤a_i<10^5 (1≤i≤N)

a_i is an integer.

Input

The input is given from Standard Input in the following format:

N
a_1 a_2 .. a_N

Output

Print the maximum possible number of i such that a_i=X.

Sample Input 1

7
3 1 4 1 5 9 2

Sample Output 1

4

For example, turn the sequence into 2,2,3,2,6,9,2 and select X=2 to obtain 4, the maximum possible count.

Sample Input 2

10
0 1 2 3 4 5 6 7 8 9

Sample Output 2

3

Sample Input 3

1
99999

Sample Output 3

1

Solution in Python (3.4.3) (judge verdict: Time Limit Exceeded)

#https://atcoder.jp/contests/abc072/tasks/arc082_a

from functools import reduce
n = int(input())
l = list(map(int, input().split()))

def get_process(arg):
    def process(accumulator, currentValue):
        if currentValue == arg or currentValue+1 == arg or currentValue-1 == arg:
            return accumulator + 1
        else:
            return accumulator
    return process

rl = [0 for _ in range(n)]
for i in range(n):
    for option in range(-1, 2):
        rl[i] = (reduce(get_process(l[i]+option), l, 0))

print(max(rl))