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<bits/stdc++.h>

#define int int64_t
#define rep(i,a,n) for(int i=(a); i<(n); ++i)
#define gsort(x,n) sort((x),(x)+(n),greater<int>())
#define all(x) (x).begin(), (x).end()
#define re(s) reverse((s).begin(),(s).end())
#define ll long long
#define setout(n,x) setw(n) << setfill(x)
#define Fixed fixed << setprecision(10)
const int INF = 0x3f3f3f3f;
const int LINF = 0x3f3f3f3f3f3f3fLL;
const int mod = 1000000007;
using namespace std;

int a[100010];
signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    int n,cnt=0;
    cin>>n;
    int x;

    rep(i,0,n){
        cin>>x;
        ++x;
        ++a[x];
        ++a[x-1];
        ++a[x+1];
        cnt = max(cnt,max(a[x],max(a[x+1],a[x-1])));
    }
    cout<<cnt<<'\n';
}