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)

// ProblemURL : https://atcoder.jp/contests/abc072/tasks/abc072_c
// ---------------------------------------------
package main

import "fmt"

func main() {
	var n int
	fmt.Scan(&n)
	as := make([]int, n)
	for i := range as {
		fmt.Scan(&as[i])
	}
	cts := make([]int, 1e5+10)
	for _, a := range as {
		if a-1 >= 0 {
			cts[a-1]++
		}
		cts[a]++
		cts[a+1]++
	}

	mx := 0
	for i := range cts {
		if cts[i] > mx {
			mx = cts[i]
		}
	}
	fmt.Println(mx)
}