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: Wrong Answer)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <math.h>

/*
int sort(const void *a, const void *b){
    return *(int*)a-*(int*)b ;
}
    qsort (a,n,sizeof(int),sort);   */



int main(void){
    int n;
    scanf("%d",&n);
    int a[n],max=0;
    for (int i=0; i<n; i++){
        scanf("%d",&a[i]);
        if (a[i]>max){
            max=a[i]+1;
        }
    }
    int count[max];
    for (int i=0; i<max; i++){
        count[i]=0;
    }
    for(int i=0; i<n; i++){
        count[a[i]]++;
    }
    int tmp=0;
    for (int i=1; i<max-1; i++){
        if(count[i-1]+count[i]+count[i+1]>tmp){
            tmp=count[i-1]+count[i]+count[i+1];
        }
    }
    printf("%d\n",tmp);
	return 0 ;
}