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 (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#define PI 3.141592653589793
#define MOD 1000000007

long int combination(long int n, long int r);

//qsort用、昇順
int compare_int(const void *a, const void *b)
{
	return *(int*)a-*(int*)b;
}
//qsort(data, 10, sizeof(int), compare_int)

long int combination(long int n, long int r)
{
	if(r>n-r) r = n-r;
	if(r == 0) return 1;
	else if(r == 1) return n;
	return (combination(n-1, r) + combination(n-1, r-1));
	//大きくなるとき
	/*
	long int tmp1, tmp2, tmp3;
	tmp1 = combination(n-1, r);
	if(tmp1>=MOD) tmp1 = tmp1%MOD;
	tmp2 = combination(n-1, r-1);
	if(tmp2>=MOD) tmp2 = tmp2%MOD;
	tmp3 = tmp1+tmp2;
	if(tmp3>=MOD) tmp3 = tmp3%MOD;
	return (tmp3);
	*/
}


int main(){
	int n;
	scanf("%d", &n);
	int array[100001];
	for(int i=0; i<n; i++){
		scanf("%d", &array[i]);
	}

	int la=array[0], sm=array[0];
	for(int i=0; i<n; i++){
		if(la<array[i]) la = array[i];
		if(sm>array[i]) sm = array[i];
	}
	//qsort(array, n, sizeof(int), compare_int);
	int count, max=0;
	for(int x=sm; x<=la; x++){
		count=0;
		for(int i=0; i<n; i++){
			if(abs(array[i]-x)<=1) count++;
		}
		if(count>max) max = count;
	}

	printf("%d\n", max);

	return 0;
}