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: Wrong Answer)

// BY KUTBILIM
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main(){
//	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	int n;cin >> n;
	int a[n];
	int c[100000] = {0,};
	for(int i = 0; i < n; i++){
		cin >> a[i];
		if(a[i] != 0){
			c[a[i]-1]++;
			c[a[i]+1]++;
			c[a[i]]++;
		}else{
			c[a[i]+1]++;
			c[a[i]]++;
		}
	}
	int mx = 0;
	for(int i = 1; i <= 100000; i++){
		mx = max(mx,c[i]);
	}
	cout << mx;
	return 0;
}