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)

// C - Together
#include <bits/stdc++.h>
using namespace std;
using vi = vector<int>;
#define rp(i,s,e) for(int i=(s);i<(e);++i)

void vprn(vector<int> &v){ for(int i=0;i<v.size();i++) cout<<v[i]<<(i<v.size()-1?",\t":"\n"); }

int main(){
	int N; cin>>N;
	vi C(100000+1);
	int a,b,c, cmax = 0;
	rp(i, 0, N){
		cin>>a; C[a]++;
		cmax = max(cmax, a);
	}
	C.resize(max(3, cmax+1));
	// vprn(C);//

	int ans = 0;
	rp(x, 1, C.size()-1){
		ans = max(ans, C[x-1] + C[x] + C[x+1]);
	}
	cout<< ans <<endl;
}