#define TEST_MODE true
 
#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
 
#include "bits/stdc++.h"
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define rep2(i, a, b) for (int i = (a); i < (int)(b); ++i)
#define rrep(i, n) for (int i = (n)-1; i >= 0; --i)
#define rrep2(i, a, b) for (int i = (a)-1; i >= (int)b; --i)
#define range(i, a, b, c) for (int i = a;		\
                               c > 0 ? i < b : i > b;	\
                               i += c)
#define chmax(a, b) (a = (a) < (b) ? (b) : (a))
#define chmin(a, b) (a = (a) > (b) ? (b) : (a))
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define all(a) begin(a), end(a)
#define ifnot(a) if (not(a))
#define int long long
 
#if TEST_MODE == true
const bool test = true;
#define dump(x) cerr << #x << " = " << (x) << " "
#define dumpl(x) cerr << #x << " = " << (x) << " " << endl;
#else
const bool test = false;
#define dump(x) 
#define dumpl(x) 
#endif
 
int dx[] = {1, 0, -1, 0};
int dy[] = {0, 1, 0, -1};
const int INF = (int)1 << 60;
const ll INFL = (ll)1 << 60;
ll mod_n = (int)1e9 + 7;
const double eps = 1e-10;
typedef long double Real;
// return -1, 0, 1
int sgn(const Real &r) { return (r > eps) - (r < -eps); }
int sgn(const Real &a, const Real &b) { return sgn(a - b); }
 
//.....................
const int MAX = (int)2e5 + 5;
 
vector<string> split(const string &str, char sep)
{
  vector<string> v;
  stringstream ss(str);
  string buffer;
  while (getline(ss, buffer, sep))
    {
      v.push_back(buffer);
    }
  return v;
}
 
template <class InputIterator>
int sum(InputIterator begin, InputIterator end)
{
  return accumulate(begin, end, 0ll);
}
 
template<typename T>
T gcd(T a, T b)
{
  T c;
  while (a != 0) {
    c = a; a = b%a;  b = c;
  }
  return b;
}
 
void solve();
 
class Solver {
public:
  int N;
  vector<int> a;
  
  // int ans() {
  //   sort(all(a));

  //   int pre1_id = -1;
    
  //   int cur_v = 0;

  //   rep(i, a.size()) {
      
  //     if (cur_v != a[i]) {
  // 	if (pre_id = -1) {
  // 	  pre_id = 0;
  // 	}
	
  //     }

      
  //   }
    
    
  //   return final_ans;
  // }

  int ans() {
    sort(all(a));
    
    int cur_ans = 0;
 
    int max_v = *max_element(all(a));
    
    rep2(i, -1, max_v + 5) {
 
      // dumpl(i);
      // dumpl(upper_bound(all(a), i + 1) - a.begin());
      // dumpl(lower_bound(all(a), i - 1) - a.begin());

      int cnt = 0;
      
      rep(j, 3) {
	cnt += upper_bound(all(a), i + j) - lower_bound(all(a), i + j);
      }

      dumpl(i);
      dumpl(cnt);
      
      cur_ans = max(cur_ans, cnt);
    }
    int final_ans = cur_ans;
    return final_ans;
  }
 
  void solve() {
    cin >> N;
    a.resize(N);
    rep(i, N) cin >> a[i];
    cout << ans() << endl;
  }
};
 
signed main()
{
  srand(time(NULL));
  cout << fixed << setprecision(20);
  auto ptr = new Solver();
  ptr->solve();
  delete ptr;
  // while (true) {    
  //     auto ptr = new Solver();
  //     ptr->solve();
  //     delete ptr;
  // }
  return 0;
}
 
// class Mycin {
// 	bool flag = true;
// public:
// 	Mycin& operator >> (int& a) {flag = scanf("%lld", &a) != EOF; return *this;}
// 	Mycin& operator >> (char& a) {flag = scanf("%c", &a) != EOF; return *this;}
// 	Mycin& operator >> (string& s) {flag = (bool)(cin >> s); return *this;}
// 	operator bool() {return flag;}
// } mycin;
 
// class Mycout {
// public:
// 	Mycout& operator << (const int& a) {printf("%lld", a); return *this;}
// 	Mycout& operator << (const char c) {printf("%c", c); return *this;}
// 	Mycout& operator << (const string& s) {printf("%s", s.c_str()); return *this;}
// } mycout;
 
// #define cin mycin
// #define cout mycout
// #define endl '\n'


Measured memory_bytes: 1152