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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <algorithm>
#include <vector>
#include <iostream>
#include <limits.h>
#include <math.h>
#include <unordered_map>
#include <assert.h>
using namespace std;

#define ran(i, a, b) for ((i) = (a); (i) < (b); (i)++)
#define rep(i, a) ran ((i), 0, (a))
#define rep1(i, a) ran ((i), 1, (a)+1)
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef long long ll;
#define _0 first
#define _1 second
#define _pb(x) push_back(x)
#define _mp(x, y) make_pair(x, y)
#if defined(SHIROKO1_LOCAL) && !defined(NDEBUG)
#define DEBUG(...) fprintf(stderr, "[DEBUG] " __VA_ARGS__)
#else
#define DEBUG(...) ((void)0)
#endif



int main()
{
	int N;
	static int A[100100];
	static int f[100100];
	static const int ofs = 3;
	cin >> N;
	int i;
	rep (i, N) {
		cin >> A[i];
		A[i] += ofs;
	}
	rep (i, N) {
		f[A[i]-1]++;
		f[A[i]]++;
		f[A[i]+1]++;
	}
	int ans = -1;
	rep (i, 100100)
		ans = max(ans, f[i]);
	cout << ans << endl;
	return 0;
}