Problem p00222 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, s, n) for (int i = s; i < (int)n; i++)
#define per(i, n) for (int i = n; i >= 0; i--)
#define ROF(i, s, n) for (int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\\n"
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n)                                                             \\
  for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define CLR(a) memset((a), 0, sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\\n";
#define debug(x)                                                               \\
  cout << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << "\\n";
#define sq(n) (n) * (n)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue<int, vector<int>, greater<int>> minpq;
static const double EPS = 1e-10;
static const double PI = acos(-1.0);
static const int mod = 10007;
static const int INF = 1 << 25;
static const LL LL_INF = 1152921504606846976;
static const int dx[] = {-1, 0, 1, 0, 1, -1, 1, -1};
static const int dy[] = {0, -1, 0, 1, 1, 1, -1, -1};

VI pm;
int n;

int main() {
  vector<bool> is_pm(10000000, true);
  for (int i = 3; i * i <= 10000000; i += 2) {
    if (is_pm[i]) {
      for (int j = i * i; j < 10000000; j += i) {
        is_pm[j] = false;
      }
    }
  }
  while (~scanf("%d", &n) && n) {
    if (n % 2 == 0) {
      n--;
    }
    for (int i = n; i >= 13; i -= 2) {
      if (is_pm[i] && is_pm[i - 2] && is_pm[i - 6] && is_pm[i - 8]) {
        printf("%d\\n", i);
        break;
      }
    }
  }
  return 0;
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
#define FOR(i, s, n) for (int i = s; i < (int)n; i++)
#define per(i, n) for (int i = n; i >= 0; i--)
#define ROF(i, s, n) for (int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\\n"
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n)                                                             \\
  for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s, e) ((s).find(e) != (s).end())
#define SORT(c) sort((c).begin(), (c).end())
#define CLR(a) memset((a), 0, sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\\n";
#define debug(x)                                                               \\
  cout << #x << " = " << (x) << " (L" << __LINE__ << ")"                       \\
       << " " << __FILE__ << "\\n";
#define sq(n) (n) * (n)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue<int, vector<int>, greater<int>> minpq;
static const double EPS = 1e-10;
static const double PI = acos(-1.0);
static const int mod = 10007;
static const int INF = 1 << 25;
static const LL LL_INF = 1152921504606846976;
static const int dx[] = {-1, 0, 1, 0, 1, -1, 1, -1};
static const int dy[] = {0, -1, 0, 1, 1, 1, -1, -1};

VI pm;
int n;
bool is_pm[10000000] = {false};

int main() {
  bool can_add;
  for (int i = 3; i < 10000000; i += 2) {
    can_add = true;
    for (int j = 0; j < pm.size() && sq(pm[j]) <= i; ++j) {
      if (i % pm[j] == 0) {
        can_add = false;
        break;
      }
    }
    if (can_add) {
      pm.push_back(i);
      is_pm[i] = true;
    }
  }
  while (~scanf("%d", &n) && n) {
    if (n % 2 == 0) {
      n--;
    }
    for (int i = n; i >= 13; i -= 2) {
      if (is_pm[i] && is_pm[i - 2] && is_pm[i - 6] && is_pm[i - 8]) {
        printf("%d\\n", i);
        break;
      }
    }
  }
  return 0;
}