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 <sstream>
#include <iostream>
#include <math.h>
#include <time.h>
#include <unistd.h>
#include <algorithm>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <set>
#include <string>

#ifndef ONLINE_JUDGE
	#define DEBUG(x) cout << '>' << #x << ':' << x << endl;
#else
	#define DEBUG(x) do {} while(0);
#endif

#define pb push_back
#define mp make_pair
#define X first
#define Y second
#define FOR(i, A, N) for(int (i) = (A); (i) < (N); (i)++)
#define REP(i, N) for(int (i) = 0; (i) < (N); (i)++)

using namespace std;
typedef long long ll;
inline bool EQ(double a, double b) { return fabs(a-b) < 1e-9; }

int n,m;
int cnt[111111];

int main() {
	scanf("%d", &n);
	REP(i, n) {
		int x;
		scanf("%d", &x);
		cnt[x]++;
	}
	int ans = 0;
	for(int X = 1; X <= 100000; X++) {
		ans = max(ans, (cnt[X]+cnt[X-1]+cnt[X+1]));
	}
	printf("%d\n", ans);
	return 0;
}