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 <iostream>
#include <string>
#include <algorithm>
#include <cmath>
#include <numeric>
using namespace std;
#define inf 1000000007

int main(void){
    int n;
    cin >> n;
    int a[n];
    int check[10001];
    int ans = 0;
    for(int i = 0; i <= 10000; i++)
        check[i] = 0;
    for(int i = 0; i < n; i++){
        cin >> a[i];
        check[a[i]]++;
    }
    for(int i = 1; i <= 10000; i++)
        ans = max(ans, check[i-1]+check[i]+check[i+1]);
    cout << ans << endl;
    return 0;
}