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>
#include <vector>

using namespace std;

#define MAX_N 10000000

bool sosuu[MAX_N+1];
int main() {
//	vector<int> s;

	fill(&sosuu[0], &sosuu[MAX_N], true);
	sosuu[0] = sosuu[1] = false;

	for (int i = 2; i < MAX_N+1; ++i)
		if (sosuu[i]) {
//			s.push_back(i);
			for (int j = i*2; j < MAX_N+1; j += i)
				sosuu[j] = false;
		}

	int n;
	while (cin >> n, n) {
		for (int i = n; i >= 13; --i)
			if (sosuu[i] && sosuu[i-2] && sosuu[i-6] && sosuu[i-8]) {
				cout << i << endl;
				break;
			}
	}
}

C++: #include <cstdio>
#include <iostream>
#include <string>
#define N 10000001
using namespace std;

int main(){
  int i,j,n;
  bool a[N];
  for(i=2;i<N;i++) a[i] = 1;
  for(i=2;i*2<=N;i++){
    if(a[i] == 1){
      for(j=i*2;j<=N;j+=i) a[j] = 0;
    }
  }

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

    int ans = 0;
    for(i=n;i>=13;i--){
      if(a[i] == 1 && a[i-2] == 1 && a[i-6] == 1 && a[i-8] == 1){
	ans = i;
	break;
      }
    }

    cout << ans << endl;

  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
 
bool prime[10000005];
vector < int > yotsugo;
 
int main()
{
    int N;
    fill_n(prime, 10000005, true);
 
    for ( int i = 2; i < 3335; i++ ) {
        if ( prime[i] ) {
            for ( int j = i * i; j < 10000005; j += i ) {
                prime[j] = false;
            }
        }
    }
    for ( int i = 5; i <= 10000000 - 8; i++ ) {
        if ( prime[i] && prime[i + 2] && prime[i + 6] && prime[i + 8] ) {
            yotsugo.push_back(i + 8);
        }
    }
 
    while ( cin >> N , N != 0 ) {
        cout << *(upper_bound(yotsugo.begin(), yotsugo.end(), N) - 1) << endl;
    }
 
    return ( 0 );
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cctype>
#include<utility>
#include<string>
#include<cmath>
#include <numeric>
#include<map>
 
 
#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define llong long long
#define pb(a) push_back(a)
#define INF 1e13
using namespace std;
typedef pair<int, int> P;
typedef pair<llong, llong> LP;
typedef pair<int, P> PP;
typedef pair<llong, LP> LPP;
 
typedef long long int ll;
#define MOD 1000000007


/*nまでの素数を列挙して配列に保持*/
vector<int> Eratosthenes(int n,vector<int>& arr){

	for(int i = 0; i < n;i++){
		arr[i] = 1;
    }
    arr[0] = arr[1] = 0;

	for(int i = 2; i < sqrt(n); i++){
		if(arr[i]){
			for(ll j = 0; i * (j + 2) < n; j++){
				arr[i *(j + 2)] = 0;
			}
		}
    }
    return arr;
}


int main(){


    int n;
    int tmp = 10000000;
    vector<int> arr(tmp);


    arr = Eratosthenes(tmp,arr);/*50000までの素数を列挙*/    
   
    while(cin >> n,n){
        while(n-8>=2){

            if(arr[n] && arr[n-2] && arr[n-6] && arr[n-8]){
                cout << n << endl;
                break;
            }else{
                n--;
            }
        }
    }  
    
    
    return 0;
}