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)

N = int(input())
A = sorted(list(map(int, input().split(' '))))
A2 = list(set(A))
ans = 0
for a in A2:
    m1 = A.count(a-2)
    m2 = A.count(a-1)
    m3 = A.count(a)
    m4 = A.count(a+1)
    m5 = A.count(a+2)
    tmp1 = m1+m2+m3 
    tmp2 = m2+m3+m4 
    tmp3 = m3+m4+m5 
    tmp4 = max(tmp1, tmp2, tmp3)
    if tmp4 > ans:
        ans = tmp4
    if a-1 in A2:
        A2.remove(a-1)
    if a in A2:
        A2.remove(a)
    if a+1 in A2:
        A2.remove(a+1)
print(ans)