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 <cmath>

using namespace std;

static const int MAX_N = 10000001;
int P[MAX_N];

void prime();

int main(int argc, char** argv)
{
	prime();

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

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

void prime()
{
	for(int i=0; i<MAX_N; i++)
	{
		P[i] = 1;
	}

	int limit;
	limit = (int)sqrt((double)MAX_N);
	for(int i=2; i<=limit; i++)
	{
		if(P[i]==1)
		{
			for(int j=(i<<2); j<=MAX_N; j+=i)
			{
				P[j] = 0;
			}
		}
	}
}

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

#define MAX 1000000

int main(){
  bool arr[MAX];
  for(int i=0;i<MAX;i++){
    arr[i] = 1;
  }
  for(int i=2;i<sqrt(MAX);i++){
    if(arr[i]){
      for(int j=0;i*(j+2) < MAX;j++){
	arr[i*(j+2)] = 0;
      }
    }
  }
  while(1){
    int a;
    cin >> a;
    if(a == 0) break;
    for(int i=a;i>=0;i--){
      if(arr[i] == 1){
	if(arr[i-2] == 1){
	  if(arr[i-6] == 1){
	    if(arr[i-8] == 1){
	      cout << i << endl;
	      break;
	    }
	  }
	}
      }
    }
  }
}

C++: #include<stdio.h>
#include<math.h>
#include<iostream>
using namespace std;

int main(){
	int p[100],n,i,j,k,a,c=0,t=1;
	scanf("%d", &n);
	while (n>0){
	if (n % 2 == 0){
		n=n - 1;
	}
		for (i = n; i > 1; i-=2){
			for (j = 3; j < sqrt(i); j+=2){
				if (i%j == 0){
					t = 0;
					break;
				}
			}
				if (t==1){
					p[c] = i;
					c++;
				}
				t = 1;
		}
		for (i = 0; i < c-3;i++){
			if (p[i] - 2 == p[i + 1] && p[i] - 6 == p[i + 2]&&p[i]-8&&p[i+3]){
				printf("%d\n",p[i]);
				break;
			}
		
		}
		scanf("%d",&n);
	}
}

C++: #include<bits/stdc++.h>
using namespace std;
#define EPS 1e-14
int main()
{
	while(true){
		int N;
		scanf("%d",&N);
		if(N==0)break;
		if(N>=13&&N<=18){
			printf("13\n");
			continue;
		}
		while(true){
			if(N%10!=9){
				N--;
				continue;
			}
			bool F=true;
			int p=N;
			for(int i=2;i*i<=p;i++){
				if(p%i==0)F=false;
			}
			if(!F)goto next;
			for(int i=2;i*i<=p-2;i++){
				if((p-2)%i==0)F=false;
			}
			if(!F)goto next;
			for(int i=2;i*i<=p-6;i++){
				if((p-6)%i==0)F=false;
			}
			if(!F)goto next;
			for(int i=2;i*i<=p-8;i++){
				if((p-8)%i==0)F=false;
			}
			if(!F)goto next;
			next:;
			if(F){
				printf("%d\n",N);
				break;
			}
			else N-=10;
		}
	}
	return 0;
}

C++: #include <cstdio>
#include <cstdlib>
#include <cstring>
#include <climits>
#include <cmath>
#include <ctime>
#include <cassert>
#include <iostream>
#include <fstream>
#include <sstream>
#include <iomanip>
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <deque>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <iterator>
#include <functional>
#include <utility>
#include <algorithm>
#include <numeric>
#include <typeinfo>

using namespace std;

#define dump(n) cerr<<"# "<<#n<<"="<<(n)<<endl
#define repi(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,n) repi(i,0,n)
#define iter(c) __typeof((c).begin())
#define foreach(i,c) for(iter(c) i=(c).begin();i!=(c).end();++i)
#define allof(c) (c).begin(),(c).end()
#define mp make_pair

typedef unsigned int uint;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<string> vs;
typedef pair<int,int> pii;

int main()
{
	const int N=10000000;
	bool* isp=new bool[N+1];
	fill(isp,isp+N+1,true);
	isp[0]=isp[1]=0;
	rep(i,N+1) if(isp[i]) for(int j=i+i;j<=N;j+=i)
		isp[j]=false;
	vi ps;
	rep(i,N+1) if(isp[i])
		ps.push_back(i);
	delete[] isp;
	
	for(int n;cin>>n,n;){
		int res=0;
		for(int i=3;ps[i]<=n;i++)
			if(ps[i]-ps[i-3]==8)
				res=ps[i];
		cout<<res<<endl;
	}
	
	return 0;
}