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, i, x, a, temp int 
    ans:=1
    fmt.Scan(&n)
    c:=make([]int, 100000)
    for i=0;i<n;i++{
      fmt.Scan(&a)
      c[a]++
    }
    // c[b] = a[i] == b なる i の個数

    for x=1;x<99999;x++{
      temp=c[x-1]+c[x]+c[x+1]
      if temp>ans{
        ans=temp
      }
    }
  fmt.Println(ans)
}