#include <bits/stdc++.h>
using namespace std;
const int nmax = 10000000;
char nums[nmax];
int main() {
  int n;
  for (int i = 2; i < nmax; i++) {
    nums[i] = '1';
  }
  for (int i = 2; i * i < nmax; i++) {
    for (int k = 2; k * i < nmax; k++) {
      nums[i * k] = '0';
    }
  }
  while (cin >> n) {
    if (n == 0) break;
    int i = n;
    while (nums[i] == '0' || nums[i - 2] == '0' || nums[i - 6] == '0' ||
           nums[i - 8] == '0')
      i--;
    cout << i << endl;
  }
  return 0;
}
