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 JavaScript (node.js v5.12) (judge verdict: Accepted)

"use strict"
function Main(input) {
  input = input.trim().split('\n');
  const N = Number(input[0].trim());
  const A = input[1].trim().split(' ').map(Number);

  if(N === 1) {
    console.log('1');
    return;
  }

  let ret = {};
  for(let n of A){
    ret[n - 1] = ret[n - 1] ? ret[n - 1] + 1 : 1;
    ret[n] = ret[n] ? ret[n] + 1 : 1;
    ret[n + 1] = ret[n + 1] ? ret[n + 1] + 1 : 1;
  }
  
  let ans = 0;
  Object.keys(ret).map((k) => {
    if(ret[k] > ans) ans = ret[k];
  })

  console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));