Go: package main

import "fmt"

func main() {
	var i int64
	var list = []int64{13, 19, 109, 199, 829, 1489, 1879, 2089, 3259, 3469, 5659, 9439, 13009, 15649, 15739, 16069, 18049, 18919, 19429, 21019, 22279, 25309, 31729, 34849, 43789, 51349, 55339, 62989, 67219, 69499, 72229, 77269, 79699, 81049, 82729, 88819, 97849, 99139, 101119, 109849, 116539, 119299, 122209, 135469, 144169, 157279, 165709, 166849, 171169, 187639, 194869, 195739, 201499, 201829, 217369, 225349, 240049, 243709, 247609, 247999, 257869, 260419, 266689, 268819, 276049, 284749, 285289, 294319, 295879, 299479, 300499, 301999, 326149, 334429, 340939, 346399, 347989, 354259, 358909, 361219, 375259, 388699, 389569, 392269, 394819, 397549, 397759, 402139, 402769, 412039, 419059, 420859, 427249, 442579, 444349, 452539, 463459, 465169, 467479, 470089, 477019, 490579, 495619, 500239, 510619, 518809, 536449, 536779, 539509, 549169, 559219, 563419, 570049, 572659, 585919, 594829, 597679, 607309, 622249, 626629, 632089, 632329, 633469, 633799, 654169, 657499, 661099, 663589, 664669, 666439, 680299, 681259, 691729, 705169, 715159, 734479, 736369, 739399, 768199, 773029, 795799, 803449, 814069, 822169, 823729, 829729, 833719, 837079, 845989, 854929, 855739, 857959, 875269, 876019, 881479, 889879, 907399, 930079, 938059, 946669, 954979, 958549, 959479, 976309, 978079, 983449, 1002349, 1003369, 1006309, 1006339, 1008859, 1015369, 1022389, 1022509, 1023949, 1027759, 1043599, 1063969, 1065019, 1068259, 1068709, 1091269, 1093069, 1093999, 1100839, 1117609, 1117819, 1118869, 1120549, 1121839, 1122139, 1126669, 1137889, 1146799, 1155619, 1156039, 1157839, 1163719, 1167709, 1168249, 1170139, 1172029, 1172539, 1173589, 1182289, 1210879, 1228399, 1230379, 1233439, 1246249, 1246369, 1257079, 1272289, 1285519, 1298119, 1322179, 1322599, 1324579, 1329709, 1337269, 1339909, 1340329, 1351249, 1352209, 1358809, 1360789, 1368469, 1381279, 1400809, 1402369, 1410979, 1440589, 1447009, 1451839, 1461409, 1468639, 1508629, 1514329, 1524079, 1525969, 1540969, 1571749, 1573549, 1573939, 1577299, 1584439, 1588759, 1592869, 1603339, 1615849, 1616809, 1621729, 1627609, 1631059, 1653109, 1659109, 1670569, 1678759, 1681879, 1685449, 1691869, 1711819, 1718869, 1727779, 1747729, 1748479, 1749499, 1755829, 1764229, 1780489, 1791739, 1797379, 1798639, 1802659, 1819849, 1830349, 1833529, 1834039, 1837399, 1857679, 1890529, 1902619, 1904479, 1910269, 1912069, 1912459, 1915939, 1917739, 1925389, 1943659, 1954159, 1954369, 1959319, 1979149, 1979899, 2002339, 2007619, 2007919, 2016409, 2020729, 2050339, 2062009, 2063779, 2065579, 2075839, 2079199, 2083519, 2084449, 2087389, 2107669, 2116579, 2136139, 2141809, 2143489, 2144509, 2157739, 2159239, 2168659, 2176639, 2177509, 2193889, 2202799, 2203969, 2223679, 2225059, 2246149, 2248249, 2256349, 2262979, 2266639, 2289649, 2290039, 2294059, 2303599, 2340259, 2342779, 2362279, 2373409, 2376169, 2381089, 2403889, 2413429, 2418679, 2423419, 2443789, 2458669, 2470339, 2478529, 2479669, 2499949, 2508049, 2535109, 2541949, 2546239, 2552119, 2552659, 2561269, 2564329, 2576599, 2594959, 2594989, 2596669, 2604739, 2614069, 2635489, 2668249, 2673529, 2674549, 2679499, 2683789, 2696929, 2704909, 2712379, 2715289, 2728549, 2731699, 2731909, 2759299, 2761729, 2764129, 2790259, 2805169, 2822719, 2839939, 2840269, 2846869, 2849689, 2875339, 2879299, 2893489, 2918569, 2927599, 2927809, 2952799, 2954689, 2989039, 2990839, 3047419, 3058879, 3062209, 3063499, 3066829, 3076399, 3089329, 3092569, 3101479, 3103279, 3129619, 3153589, 3157579, 3171739, 3187609, 3200209, 3207439, 3208819, 3215749, 3224869, 3243349, 3277699, 3295549, 3308959, 3326629, 3328909, 3340879, 3366829, 3371449, 3374479, 3378049, 3400219, 3416059, 3436249, 3437719, 3467539, 3479899, 3512059, 3512239, 3512989, 3513079, 3514549, 3518329, 3550699, 3584929, 3586909, 3593509, 3621469, 3652939, 3669769, 3690529, 3713449, 3727729, 3735169, 3741169, 3798079, 3817819, 3837139, 3837859, 3849829, 3854119, 3894049, 3919219, 3919

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long; using ull = unsigned long long;
//#define int ll
using vb = vector<bool>; using vvb = vector<vb>;
using vi = vector<int>; using vvi = vector<vi>;
using vl = vector<ll>; using vvl = vector<vl>;
template<class T> using V = vector<T>;
template<class T> using VV = vector<V<T>>;
#define fi first
#define se second
#define maxs(x,y) (x=max(x,y))
#define mins(x,y) (x=min(x,y))
using pii = pair<int,int>; using pll = pair<ll,ll>;
#define FOR(i,a,b) for(ll i = (a); i < (ll)(b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RFOR(i,a,b) for(ll i = (ll)(b)-1;i >= a;--i)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(obj) (obj).begin(), (obj).end()
#define rALL(obj) (obj).rbegin(), (obj).rend()
#define eb(val) emplace_back(val)
const double PI = acos(-1), EPS = 1e-10;
const ll MOD = 1e9+7;
pair<vl,vb> eratosthenes_sieve(ll n){
  vb is_prime(n+1,true);
  vl prime;
  is_prime[0] = false;
  is_prime[1] = false;
  FOR(i,2,sqrt(n)+1){
    if(!is_prime[i]) continue;
    for(ll j=2*i;j<=n;j+=i) is_prime[j] = false;
    prime.eb(i);
  }
  FOR(i,sqrt(n)+1,n+1){
    if(is_prime[i])prime.eb(i);
  }
  return {prime,is_prime};
}
signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  auto ppp = eratosthenes_sieve(1e7+1);
  auto pt = ppp.second;
  vl dp(1e7+1,0);
  FOR(i,2,1e7-6){
    if(pt[i]&&pt[i+2]&&pt[i+6]&&pt[i+8]) dp[i+8] = i+8;
    else dp[i+8] = dp[i+7];
  }
  while(cin >> n,n){
    cout << dp[n] << endl;
  }
}

C++: import java.util.Scanner;

public class Main{
    public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	int n = 0,maxPQ = 0;
	
	while(sc.hasNext()){
	    n = sc.nextInt();
	    if(n==0) break;
	    
	    boolean[] check = new boolean[n];

	    System.out.println(checkPrime(check));
	}
    }

    static int checkPrime(boolean[] check){ // テ・ツ崢崚」ツ?、テ・ツュツ静ァツエツ?ヲツ閉ーテ」ツつ津ィツソツ氾」ツ??
	
	for(int i = 1;i*i<check.length;i++){ // テ」ツ?敕」ツつ古」ツ?古ァツエツ?ヲツ閉ーテ」ツ??」ツ?」テ」ツ?淌」ツつ嘉」ツ?敕」ツ?ョテ・ツ?催ヲツ閉ーテ」ツつ断alseテ」ツ?ォテ」ツ?凖」ツつ?
	    if(!primeNum(i+1)) notPrime(check,i+1);
	}

	for(int i = check.length-1;i>=0;i--){ // trueテ」ツつ津」ツ?ソテ」ツ?、テ」ツ?妥」ツ?淌」ツつ嘉」ツ?敕」ツ?ョテ、ツクツ凝」ツ?ィテ」ツ?凝」ツつづィツヲツ凝」ツ?ヲテ」ツ?｛kテ」ツ??」ツ?」テ」ツ?淌」ツつ嘉」ツ?敕」ツつ古」ツ?古ヲツ慊?・ツ、ツァテ」ツ?ョテヲツ閉ーテ」ツ??」ツ?療ィツソツ氾」ツ?療」ツ?。テ」ツつε」ツ??
	    if(!check[i] && !check[i-2] && !check[i-6] && !check[i-8]){
		return i+1;
	    }
	}

	return 0; // テ、ツサツョ
	
    }
    static boolean primeNum(int num){ // テァツエツ?ヲツ閉ーテ」ツつ津ヲツ閉ーテ」ツ?暗」ツつ?
	int count=0;
	for(int i = 1;i<=num;i++){
	    if(num%i==0) count++;
	}
	return count==2?false:true;
    }
    static void notPrime(boolean[] check,int n){ // テァツエツ?ヲツ閉ーテ」ツ??」ツ?」テ」ツ?淌ヲツ閉ーテ」ツ?ョテ・ツ?催ヲツ閉ーテ」ツつ稚rueテ」ツ?ォ
	for(int i = 2;i*n<check.length;i++){
	    check[(n*i)-1] = true;
	}
    }
}

C++: #include<iostream>

using namespace std;

int prime[100000];

void make(void);

int main(){
  make();
  while(1){
    int n;
    cin >> n;
    if(n == 0) break;

    if(n > 100000) n = 100000;
    
    for(int i = n; i >= 13; i--){
      if(prime[i] == 1 && prime[i-2] == 1 && prime[i-6] == 1 && prime[i-8] ==1){
	cout << i << endl;
	break;
      }
    }
  }
  return 0;
}

void make(void){
  for(int i = 0; i < 100000; i++) prime[i] = 1;

  prime[0] == 0;
  prime[1] == 0;

  for(int i = 2; i*i < 100000; i++){
    if(prime[i] == 1){
      for(int j = i*2; j < 100000; j+=i) prime[j] = 0;
    }
  }
}

C++: #include <cstdio>

int prmt[10000005]={};

int rest[10000005]={};

int main(void){
int n,i,j;
prmt[0]=-1;
prmt[1]=-1;
for(i=2;i<=10000000;i++){
	if(prmt[i]==-1)continue;
	prmt[i]=1;
	j=i*2;
	while(j<=10000000){
		prmt[j]=-1;
		j+=i;
	}
}
j=13;
for(i=13;i<=10000000;i++){
	if(prmt[i]==1 && prmt[i-2]==1 && prmt[i-6]==1 && prmt[i-8]==1)j=i;
	rest[i]=j;
}
while(1){
scanf("%d",&n);
if(n==0)break;
printf("%d\n",rest[n]);
}
return 0;
}