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 isPrime(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(){
	
	int n;
	int ans;
	while(true){
		ans=0;
		cin >> n;
		if(n==0)
			break;
		
		int i=n;
		while(i>=13){
				if(isPrime(i)&&isPrime(i-2)&&isPrime(i-6)&&isPrime(i-8))
								ans=i;
				if(ans!=0)
					break;
				i--;
				
			}	
		
	cout << ans << endl;
	}
	
	
	return 0;
}

C++:         cout << n << " " << p[idx] << endl;

C++: #include <bits/stdc++.h>
using namespace std;

int prime[10000005] = {1, 1};
int print[10000005] = {-1, -1, 2};

int main()
{
    long long i, j;

    for (i = 2; i * i < 10000005ll; i++) {
        if (prime[i] == 1) continue;
        for (j = 2; i * j < 10000005ll; j++) {
            prime[i * j] = 1;
        }
    }
    for (i = 13; i + 8 < 10000005; i++) {
        if (prime[i - 8] == 0 && prime[i- 2] == 0 && prime[i - 6] == 0 && prime[i] == 0) {
            print[i] = i;
        } else {
            print[i] = print[i - 1];
        }
    }

    int n;
    cin >> n;
    while (n != 0) {
        printf("%d\n", print[n]);

        cin >> n;
    }

    return 0;
}

C++: 
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>
#include<limits>
#include<iterator>

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define rep(i,n) for(int i=0; i<n; i++)
#define INF (1<<20)

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ll, char> plc;

ll n;
ll arr[10000010],ans[10000010];

void Eratosthenes() {
	for (ll i = 0; i <= n; i++)arr[i] = 1;
	
	for (ll i = 2; i <= sqrt(n); i++) {
		if (arr[i]) {
			for (ll j = 0; i*(j + 2) <= n; j++)
				arr[i*(j + 2)] = 0;
		}
	}

	ll pre_prime = 0;
	for (ll i = 13; i <= n; i++) {
		if (arr[i] && arr[i-2] && arr[i-6] && arr[i-8]) {
			ans[i] = i;
			pre_prime = i;
		}
		else ans[i] = pre_prime;
	}
}

int main()
{
	while (cin >> n, n) {
		Eratosthenes();
		cout << ans[n] << endl;
	}
	return	0;
}

C++: #include<stdio.h>
int main(void)
{
    int n,i,j,flg,w,a,b,c,d;
	while(1){
	    scanf("%d",&n);
		if(n==0) break;
		a=0;
		b=0;
		c=0;
		d=0;
		for(i=n;i>=5;i--){
		    flg=1;
		    for(j=2;j<i/2;j++){
			    w=i%j;
				if(w==0){
				    flg=0;
					break;
				}
			}
			if(flg==1){
			    d=c;
				c=b;
				b=a;
				a=i;
			}
			if(d==c+2&&d==b+6&&d==a+8) break;
		}
		printf("%d\n",d);
	}
	return 0;
}

C++: #include<iostream>

using namespace std;

char prime[9973220];

void make(void);

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

    if(n >= 9973220) n = 9973219;
    
    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 < 9973220; i++) prime[i] = 1;

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

  for(int i = 2; i*i < 9973220; i++){
    if(prime[i] == 1){
      for(int j = i*2; j < 9973220; j+=i) prime[j] = 0;
    }
  }
}

C++: #include <stdio.h>
#define MAX 10000000
int main(void){
        int i,j;
        int a[MAX+1];
        int counter;
        int n;
	counter = 0;
	for(i = 1; i <= MAX; i++){
		a[i] = 0;
	}
	for(i = 2; i <= MAX; i++){
		if(a[i]){continue;}
		for(j = i; j <= MAX; j += i){
			if(j == i){a[i] = 0;}
			else{a[j] = 1;}
		}
	}
	for(i = 2; i <= MAX; i++){
		if(!a[i]){
			counter++;
		}
	}
	while(1){
		scanf("%d",&n);
		if(n == 0){break;}
		i = n;
		while(1){
			for(; a[i]; i--){}
			if(!a[i-8] && !a[i-6] && !a[i-2]){
				printf("%d\n",i);
				break;
			}
			i--;
		}  
	}
        return 0;
}