#include <stdio.h>
#include <iostream>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <math.h>
#include <algorithm>
using namespace std;
#define ll long long
const double EPS = 1e-10;
const ll MOD = 7+(1e+9);





int main(){
  ll N=10000000;
  vector<ll> res;
  vector<bool> is_prime(N + 1, true);
  for (ll p = 2; p <= N; p++) {
    if (!is_prime[p]) continue;
    for (ll k = p * 2; k <= N; k += p) is_prime[k] = false;
    res.push_back(p);
  }
  vector<ll>v;
  for(ll i=3;i<res.size();i++){
    if(res[i-3]+2==res[i-2]&&res[i-2]+4==res[i-1]&&res[i-1]+2==res[i])v.push_back(res[i]);
  }
  ll x;
  cin>>x;
  while(x){
    cout<<*(--(upper_bound(v.begin(), v.end(),x)))<<endl;
    cin>>x;
  }

}


