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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<iostream>
#include<algorithm>
#include<cassert>
#include<vector>
#include<fstream>
#include<string>
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<queue>
#include<map>
using namespace std;
#define MOD 1000000007
#define REP(m,n) for(int i=m;i<n;++i)
#define REPj(m,n) for(int j=m;j<n;++j)
#define INF 10000000000000000
#define ll long long
#define mp make_pair

vector<int>v(100002, 0);

int main() {
	int n, ans = 0;
	cin >> n;
	REP(0, n) {
		int tmp;
		cin >> tmp;
		if (tmp == 0) {
			v[0]++;
			v[1]++;
		}
		else {
			v[tmp]++;
			v[tmp + 1]++;
			v[tmp - 1]++;
		}
	}
	REP(0, 100002) {
		ans = max(ans, v[i]);
	}
	cout << ans << endl;
	return 0;
}