#include <bits/stdc++.h>
const int N = 2e5 + 10;
int n, a[N];
inline int read() {
  int x = 0;
  char ch = getchar();
  while (!isdigit(ch)) {
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 1) + (x << 3) + (ch ^ 48);
    ch = getchar();
  }
  return x;
}
int main() {
  n = read();
  for (int i = 0; i < n; ++i) a[i] = read();
  std::sort(a, a + n);
  int ans = 1;
  std::deque<int> que;
  for (int i = 0; i < n; ++i) {
    que.push_back(a[i]);
    while (que.back() > que.front() + 5) que.pop_front();
    ans = std::max(ans, (int)que.size());
  }
  printf("%d\n", ans);
  return 0;
}
