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 <iostream>
using namespace std;
bool is_prime(int n){
	if(n<=1)
		return false;
	for(int i=2;i*i<=n;i++){
		if(n%i==0)
			return false;
	}
	return true;
}
int main(){
	while(1){
		int num;
		cin>>num;
		if(num==0)
			return 0;
		int num2=4;
		while(num2!=0){
			num2=4;
			if(is_prime(num)){
				--num2;
				if(is_prime(num-2)){
					--num2;
					if(is_prime(num-6)){
						--num2;
						if(is_prime(num-8))
							--num2;
						
					}
				}
			}
			
			if(num2!=0)
				--num;
		}
	cout<<num<<endl;
	}
	return 0;
}

C++: #include<iostream>
using namespace std;

int prime(int a) {
	if (a % 2 == 0)return false;
	if (a % 3 == 0)return false;
	for (int b = 5; b < a; b+=2) {
		if (a % b == 0)return false;
		if ((b + 1)*(b + 1) > a)return true;
	}
}
int main() {
	while (1) {
		int a;
		cin >>a;
		if (a == 0)break;
		for (int b = a - (a % 6) + 1;; b -= 6) {
			if (prime(b) && prime(b - 2) && prime(b - 6) && prime(b - 8)) { cout << b << endl; break; }
		}
	}
}

C++: //テ・ツ崢崚」ツ?、テ・ツュツ静ァツエツ?ヲツ閉ーテ」ツ?ョテ・ツ、ツァテ」ツ?催」ツ?陛」ツつ津ゥツ?催・ツ按療」ツ?ォテ・ツ?・テ」ツつ古」ツ?淌」ツつ欝ime Limit Exceededテ」ツ?ァテ」ツ?療」ツ??
//テァツ崢エテ」ツ?療」ツ?ヲテ」ツつづァツ崢エテ」ツ?療」ツ?ヲテ」ツつ５ime Limit Exceeded___テ」ツδ嘉」ツδ?」ツδ愿」ツ?ァテ」ツ??
//テ」ツつィテ」ツδゥテ」ツつケテ」ツδ暗」ツδ?」ツδ催」ツつケテ」ツ?ョテァツッツゥテ」ツつ津」ツ?凖」ツ?」テ」ツ?凝」ツつ甘・ツソツ佚」ツつ古」ツ?ヲテ」ツ??」ツ?セテ」ツ?療」ツ?淌」ツ??
// Respect2Dテ」ツ?陛」ツつ禿」ツ?ョテ」ツつウテ」ツδ。テ」ツδウテ」ツδ暗」ツつ津ィツヲツ凝」ツ?ヲテヲツーツ療」ツ?古」ツ?、テ」ツ?催」ツ?セテ」ツ?療」ツ?淌」ツ??

import java.util.*;
public class Main{
    static Scanner kbd = new Scanner(System.in);

    static int[] prime = new int[10000001];
    // 0:テヲツ慊ェテ・ツ按、テ・ツョツ?
    // 1:テァツエツ?ヲツ閉ー
    // -1:テァツエツ?ヲツ閉ーテ」ツ?ァテ」ツ?ッテ」ツ?ェテ」ツ??

    public static void main(String[] args){

	prepare();

	while(true){
	    int n = kbd.nextInt();
	    if(n==0) break;
	    solve(n);
	}
    }

    static void prepare(){
	prime[0] = prime[1] = -1;
	int i=2;
	for(; i<prime.length; i++){
	    if(prime[i] == 0){
		prime[i] = 1;
		for(int j=i+i; j<prime.length; j+=i) prime[j]=-1;
	    }
	}
    }

    static void solve(int n){

	while(!(prime[n]==1 && prime[n-2]==1 && prime[n-6]==1 && prime[n-8]==1)){
	    n--;
	}
	System.out.println(n);
    }

    /*
    static boolean prime(int a){
	int k = (int)Math.sqrt(a);
	for(int l=2; l<=k; l++){
	    if(a%l == 0) return false;
	}
	return true;
    }
    */
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<list>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<numeric>
#include<vector>
#include<cstdio>
#include<climits>
#include<cfloat>
#include<cstring>
#define foreach(t,p,it) for(t::iterator it=p.begin(),it!=p.end(),++it)
#define all(p) p.begin(),p.end()
#define rep(i,n) for(int i=0;i<n;i++)
#define REP(n) rep(i,n)
using namespace std;

#define MAXN 10000010

char prime[MAXN];
vector<int> prime4;

int main()
{
    prime[0] = 1;
    prime[1] = 1;
    for(int i=2;i<MAXN;i++) if(!prime[i])
        for(int j=2*i;j<MAXN;j+=i) prime[j] = 1;

    REP(MAXN-8)
    {
        if((!prime[i])&&(!prime[i+2])&&(!prime[i+6])&&(!prime[i+8]))prime4.push_back(i+8);
    }
    
    int n;
    int prime4num = prime4.size();
    //cout << prime4num << endl;
    while(cin>>n && n)
    {
        int ans = 0;
        REP(prime4num)
        {
            if(prime4[i]>n) break;
            if(ans<prime4[i]) ans = prime4[i];
        }
        cout << ans << endl;
    }
    

    return 0;
}

C++: #include <iostream>
using namespace std;
  int p[10000001];
int main(){

  for(int i = 2 ; i < 10000001 ; i++ )p[i] = 1;
  p[0]=p[1]=0;
  for(int i = 2 ; i*i < 10000001 ; i++ ){
    if(p[i])for(int j = i*2 ; j < 10000001 ; j+=i)p[j]=0;
  }

  int n;
  while(cin >> n, n){
    for(int i = n ; i >= 0 ; i--){
      if(p[i] == 1 && p[i-2] == 1 && p[i-6] == 1 && p[i-8] == 1){
	cout << i << endl;
	break;
      }
    }
  }
}