#include <bits/stdc++.h>
using namespace std;
long long unsigned int countDivisors(long long unsigned int n) {
  long long unsigned int cnt = 0;
  for (long long unsigned int i = 1; i <= sqrt(n); i++) {
    if (n % i == 0) {
      if (n / i == i)
        ++cnt;
      else
        cnt += 2;
    }
  }
  return cnt;
}
vector<int> v;
void Search(string pat, string txt) {
  int n = txt.size();
  int m = pat.size();
  for (int i = 0; i <= n - m; i++) {
    int j;
    for (j = 0; j < m; j++) {
      if (txt[i + j] != pat[j]) break;
    }
    if (j == m) {
      v.push_back(i);
    }
  }
  return;
}
int findFirst(const std::vector<int> &array, int key, int low, int high) {
  int ans = -1;
  while (low <= high) {
    int mid = low + (high - low) / 2;
    if (key == array[mid]) {
      ans = mid;
      high = mid - 1;
    } else if (key > array[mid])
      low = mid + 1;
    else
      high = mid - 1;
  }
  return ans;
}
int findLast(const std::vector<int> &array, int key, int low, int high) {
  int ans = -1;
  while (low <= high) {
    int mid = low + (high - low) / 2;
    if (key == array[mid]) {
      ans = mid;
      low = mid + 1;
    } else if (key > array[mid])
      low = mid + 1;
    else
      high = mid - 1;
  }
  return ans;
}
string foo(int n) {
  string ans;
  if (n >= 0 && n <= 9) {
    ans += "0";
  }
  ans += to_string(n);
  return ans;
}
int main() {
  std::ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int n;
  cin >> n;
  vector<int> arr(n);
  map<int, int> mp;
  for (int i1 = 0; i1 < n; i1++) {
    cin >> arr[i1];
    mp[arr[i1]]++;
  }
  int mx = 0, cnt = 0;
  for (int i = 0; i < n; i++) {
    cnt = mp[arr[i]];
    for (int x = arr[i] + 1; x <= arr[i] + 5; x++) {
      if (mp[x] > 0) cnt += mp[x];
    }
    mx = max(mx, cnt);
  }
  cout << mx << endl;
  return 0;
}
