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: Accepted)

#include<stdio.h>
#include<stdlib.h>
int asc(const void *a, const void *b)
{
    return *(int*)a - *(int*)b;
}
int main()
{
    int n;
    scanf("%d", &n);
    int i, j;
    int a[100005];
    for (i = 0; i < n; i++)
        scanf("%d", &a[i]);
    qsort(a, n, sizeof(int), asc);
    int ans = 0, q;
    i = 0;
    while (i < n)
    {
        q = 0;
        j = i;
        while (a[j] - a[i] < 3 && j < n)
        {
            q++;
            j++;
        }
        if (ans < q)
            ans = q;
        i++;
        while (i < n && a[i] == a[i - 1])
            i++;
    }
    printf("%d\n", ans);
    return 0;
}