//
//  main.cpp
//  101Hack44
//
//  Created by BahadirAltun on 13/12/16.
//  Copyright 2016 Bahadir Altun. All rights reserved.
//

#include <algorithm>
#include <iostream>
#include <cassert>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <string>
#include <vector>
#include <cmath>
#include <ctime>
#include <queue>
#include <stack>
#include <map>
#include <set>

using namespace std;

#define mid ((lf + rg) >> 1)
#define right (left | 1)
#define left (v << 1)

typedef pair<int, int> pii;
typedef long long ll;

const ll linf = 1e18 + 9;
const int inf = 1e9 + 9;
const int N = 1e2 + 9;

int n, a[N], h[N], ans;

int main() {

  cin >> n;

  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    h[a[i]]++;
  }

  for (int i = 1; i < N; i++)
    if (h[i] + h[i + 1] > ans)
      ans = h[i] + h[i + 1];

  cout << ans << endl;

  return 0;
}