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 <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>
#include <queue>
#define rep(i, n) for(int i = 0; i < n; i++)
#define REP(i, m, n) for(int i = m; i < n; i++)
#define ALL(v) v.begin(),v.end()
#define RALL(v) v.rbegin(),v.rend()
#define check(v) rep(i,v.size()) cout << v[i] << " ";\
cout << endl
#define INF 1e8
typedef long long ll;
using namespace std;
//オーバーフローに気をつけろよおおおおおお
//確認忘れるなよおおおおおお

int main() {
    map<int, int> m;
    int n; cin >> n;
    int ans = 0;
    rep(i,n){
        int a; cin >> a;
        m[a] += 1;
        m[a-1] += 1;
        m[a+1] += 1;
        ans = max(ans,max(m[a],max(m[a-1],m[a+1])));
    }
    cout << ans << endl;

    return 0;
}