'use strict';
const fs = require('fs');
process.stdin.resume();
process.stdin.setEncoding('utf-8');
let inputString = '';
let currentLine = 0;
process.stdin.on('data', function(inputStdin) {
inputString += inputStdin;
});
process.stdin.on('end', function() {
inputString = inputString.split('\n');
main();
});
function readLine() {
return inputString[currentLine++];
}
/*
* Complete the 'pickingNumbers' function below.
*
* The function is expected to return an INTEGER.
* The function accepts INTEGER_ARRAY a as parameter.
*/
function pickingNumbers(a) {
// Write your code here
a.sort();
let arr = []
let count ;
for(let i = 0 ; i < a.length ; i++){
count = 0
for(let j = i +1 ; j< a.length; j++){
if(Math.abs(a[i]-a[j]) <= 1){
count++
}
}
arr.push(count)
}
return Math.max(...arr) +1
}
function main() {
const ws = fs.createWriteStream(process.env.OUTPUT_PATH);
const n = parseInt(readLine().trim(), 10);
const a = readLine().replace(/\s+$/g, '').split(' ').map(aTemp => parseInt(aTemp, 10));
const result = pickingNumbers(a);
ws.write(result + '\n');
ws.end();
}
