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 <bits/stdc++.h>
using namespace std;

#define debug(x) cout<<#x<<"="<<x<<endl
#define pii pair<int,int>
#define ll long long
#define pb push_back
#define mp make_pair

int n,a,x,y;
int b[100003];

int main(){
	cin>>n;
	for (int i=0;i<n;i++){
		cin>>a;
		b[a-1]++;
		b[a+1]++;
		b[a]++;
	}
	for (int i=0;i<=100001;i++){
		if (b[i]>x) x=b[i];
	}
	cout<<x;
	return 0;
}