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: Runtime Error)

n = int(input())
a = [int(i) for i in input().split()]

a.sort()

l = list(set(a))
l_co = list()

if n == 1:
    print(1)
elif n == 2:
    if abs(a[0]-a[1]) <= 1:
        print(2)
    else:
        print(1)
else:
    for i in range(len(l)):
        l_co.append(a.count(l[i]))
    #print(l_co)
    res_l = list()
    for i in range(len(l)-2):
        res_l.append(sum(l_co[i:i+3]))
    else:
        print(max(res_l))