#include <bits/stdc++.h>
using namespace std;
bool p[10000001];
vector<int> plist, p4;
void prime() {
  p[0] = true;
  p[1] = true;
  for (int i = 4; i < 10000001; i += 2) {
    p[i] = true;
  }
  for (int i = 3; i < sqrt(10000001) + 1; i++) {
    for (int j = i * 2; j < 10000001; j += i) {
      p[j] = true;
    }
  }
  for (int i = 0; i < 10000001; i++) {
    if (!p[i]) {
      plist.push_back(i);
    }
  }
  for (int i = 0; i < plist.size() - 3; i++) {
    if (plist[i + 3] - plist[i] == 8 && plist[i + 2] - plist[i] == 6 &&
        plist[i + 1] - plist[i] == 2)
      p4.push_back(plist[i + 3]);
  }
}
int main() {
  int n;
  prime();
  while (cin >> n, n) {
    for (int i = 0; i < p4.size(); i++) {
      if (p4[i] > n) {
        cout << p4[i - 1] << endl;
        break;
      }
    }
    cout << p4[p4.size() - 1] << endl;
  }
  return 0;
}
