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>

int main(void)
{
    int i, n, a[100000], b[100002], max = 0, mix = 0;

    scanf("%d", &n);

    for(i = 0; i < n; i++) {
        scanf("%d", &a[i]);
        if(a[i] != 0)
            b[a[i] - 1]++;
        b[a[i]]++;
        b[a[i] + 1]++;
        if(max < a[i])
            max = a[i];
    }

    for(i = 0; i <= max + 1; i++) {
        if(mix < b[i])
            mix = b[i];
    }

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

    return 0;
}