#include <bits/stdc++.h>
char p[10000001];
void sieve() {
  memset(p, 1, sizeof(p));
  p[0] = p[1] = 0;
  for (int i = 2; i <= 10000000; ++i)
    if (p[i])
      for (int j = i * 2; j <= 10000000; j += i) p[j] = 0;
  return;
}
int main() {
  sieve();
  int n;
  while (std::cin >> n, n) {
    while (true) {
      if (p[n] && p[n - 2] && p[n - 6] && p[n - 8]) {
        std::cout << n << std::endl;
        break;
      }
      --n;
    }
  }
  return 0;
}
