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: Runtime Error)


#include <stdlib.h>
#include <memory.h>
#include <stdio.h>

#define MAX_LENGTH		(10000)

int main( int argc, char** argv )
{
	int a;
	int* List;
	int n;

	scanf( "%d", &n );
	if ( n > MAX_LENGTH )
		return -1;
	a = 0;
	List = malloc( sizeof( int ) * ( n + 2 ) );		// n + 2 is anti-zero
	memset( List, 0, sizeof( int ) * ( n + 2 ) );
	
	for ( int i = 0; i < n; i++ )
	{
		scanf( "%d", &a );
		List[ a - 1 ] += 1;
		List[ a     ] += 1;
		List[ a + 1 ] += 1;		// index 0 is -1
	}

// search max value
	a = 0;		// index
	
	for ( int i = 0; i < n; i++ )
	{
		if ( List[ i ] > a )
			a = List[ i ];
	}
	printf( "%d\n", a );
	return a;
}