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)

#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <numeric>
#define rep(i, m, n) for(int i = m;i < n;i++)
#define repr(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define INF 999999999
using namespace std;

int main(){
    int n; cin >> n;
    int a[n];
    rep(i, 0, n) cin >> a[i];

    SORT(a, n);

    int temp = 0;
    int ans = 0;
    rep(x, 0, a[n]+1){
        rep(i, 0, n){
            if(x == a[i] + 1) temp += 1;
            else if(x == a[i] - 1) temp += 1;
            else if(x == a[i]) temp += 1;
        }
        if(ans <= temp) ans = temp;
        temp = 0;
    }

    cout << ans << endl;

    return 0;
}