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)

int main()
{
    int n,i,a;
    int amax=0,bmax=0;
    int b[100001]={0};
    
    scanf("%d",&n);
    
    for(i=0;i<n;i++)
    {
        scanf("%d",&a);
        if(amax<a)
        {
            amax=a;
        }
        
        b[a]+=1;
        
        if(a!=0)
        {
            b[a-1]+=1;
        }
        if(a<100000)
        {
            b[a+1]+=1;
        }
    }
    
    for(i=0; i < amax+1; i++)
    {
        if(bmax<b[i])
        {
            bmax=b[i];
        }
    }
    
    printf("%d\n",bmax);
    
    return 0;
}