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: Runtime Error)

#include <bits/stdc++.h>
using namespace std;
#define repr(i,k,n) for(int i = (k); i < (n); i++)
#define rep(i,n) repr(i,0,n)
#define ALL(a) begin(a),end(a)
const int INF = 114514810;
const int MOD = 1000000007;
typedef vector<int> vi;
typedef vector<string> vs;
typedef long long ll;
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int N,p;
	int a[10000];
	int ma=0;
	cin >> N;
	rep(i,10000){
		a[i]=0;
	}
	rep(i,N){
		cin >> p;
		if(p!=0){
			a[p-1]++;
		}
		a[p]++;
		a[p+1]++;
	}
	rep(i,N){
		if(a[i]>=ma){
			ma=a[i-1];
		}
	}
	cout << ma << endl;
}