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>
using namespace std;

int n,tmp,now,nownum;
int a[100010];

inline int get_num()
{
	int now=0,fh=1;char ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-')fh=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		now=(now<<1)+(now<<3)+ch-'0';
		ch=getchar();
	}
	return now*fh;
}

int main()
{
	n=get_num();
	for(int i=1;i<=n;i++){
		tmp=get_num();
		a[tmp]++;
		a[tmp-1]++;
		a[tmp+1]++;
	}
	for(int i=1;i<=100000;i++){
		nownum=max(nownum,a[i]);
	}
	printf("%d\n",nownum);
	return 0;
}