#include <bits/stdc++.h>
using namespace std;
struct READ {
  int d1, d2, d3;
  READ(int d1 = -1, int d2 = -1, int d3 = -1) : d1(d1), d2(d2), d3(d3) {}
  template <class T>
  operator T() {
    T tmp;
    this->read(tmp);
    return tmp;
  }
  template <class T>
  void read(T& t) {
    cin >> t;
  }
  template <class T>
  void read(vector<T>& cont) {
    assert(d1 != -1);
    cont.resize(d1);
    READ r(d2, d3);
    for (int i = 0; i < d1; ++i) r.read(cont[i]);
  }
  template <class T1, class T2>
  void read(pair<T1, T2>& x) {
    read(x.first);
    read(x.second);
  }
};
static const int _ = []() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  return 0;
}();
int main(int argc, char* argv[]) {
  int n = READ();
  vector<int> skills = READ(n);
  map<int, int> h;
  for (int s : skills) {
    h[s] += 1;
  }
  int max = 0, cur = 0;
  auto itx = h.begin();
  for (auto it = h.begin(); it != h.end(); ++it) {
    while (it->first - itx->first > 5) {
      cur -= itx->second;
      ++itx;
    }
    cur += it->second;
    if (cur > max) max = cur;
  }
  cout << max << endl;
  return 0;
}
