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;
typedef long long ll;
const double EPS = 1e-9;
const int INF = 1<<29;
typedef vector<int> vint;
typedef pair<int, int> pint;
#define rep(i, n) REP(i, 0, n)
#define ALL(v) v.begin() , v.end()
#define REP(i, x, n) for(int i = x; i < n; i++)


int main(){
    int N, t; cin >> N;
    vint a(N);
    rep(i, N){
        cin >> t;
        a[t - 1]++;
        a[t]++;
        a[t + 1]++;
    }
    sort(ALL(a), greater<int>());
    cout << a[0] << endl;
    return 0;
}