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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"fmt"
)

func main(){
	var N,ma,num int
	fmt.Scan(&N)
	m := make(map[int]int)

	for i:=0;i<N;i++{
		fmt.Scan(&num)
		m[num] += 1
	}

	for key,_ := range m{
		if (m[key-1]+m[key]+m[key+1]>ma){
			ma = m[key-1]+m[key]+m[key+1]
		}
	}
	fmt.Println(ma)
}