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

Python: move = [[[10, 10], [4, 4]], [[8, 2],[4, 2]]]

MAX_N = 10000000+1
sos = [1] * (MAX_N+1)
sos[0] = sos[1] = 0
for i in range(2, int(MAX_N**0.5)+1):
    if sos[i]:
        for j in range(i+i, MAX_N+1, i):
            sos[j] = 0

while 1:
    n = int(input())

    if not n: break
    n -= (n%2 == 0)
    while n >= 13:
        if sos[n] and sos[n-2] and sos[n-6] and sos[n-8]:
            print(n)
            break
        else:
            n -= move[sos[n-8]][sos[n-6]][sos[n-2]]
# measure_stop = datetime.now()
# print(measure_stop - measure_start)

Python: from bisect import bisect_right as br

def quad_primes(n):
  is_prime = [True] * (n + 1)
  is_prime[0] = is_prime[1] = False
  for i in range(2, int(n ** (1 / 2)) + 1):
    if is_prime[i]:
      for j in range(i * i, n + 1, i):
        is_prime[j] = False

  return [i + 8 for i in range(n - 7) if is_prime[i] and is_prime[i + 2] and is_prime[i + 6] and is_prime[i + 8]]

quad = quad_primes(10000000)

while True:
  n = int(input())
  if n == 0:
    break
  print(quad[br(quad, n) - 1])

Python: def get_quad(n, p):
    for ni in range(n,0,-1):
        if p[ni] and p[ni - 2] and p[ni - 6] and p[ni - 8]:
            return ni
        
def sieve():
    n = 10000001
    p = [1] * n
    p[0] = p[1] = 0
    
    for i in range(int(n ** 0.5)):
        if p[i]:
            for j in range(2 * i, len(p), i):
                p[j] = 0
    return p
import sys
f = sys.stdin

prime = sieve()
while True:
    n = f.readline().strip()
    if not n.isdigit():
        continue
    n = int(n)
    if n == 0:
        break
    print(get_quad(n, prime))

Python: 
while True:
    ni = input().strip()
    if ni == '0':
        break
    print('0')

Python: def make_sosu_tbl():
    for i in range(2, MAX_N):
        if sos[i]:
            for j in range(i+i, MAX_N+1, i):
                sos[j] = 0
        if i**2 >= MAX_N:break

while 1:
    MAX_N = int(input())
    if not MAX_N: break
    sos = [1] * (MAX_N+1)
    make_sosu_tbl()

    for i in reversed(range(13,MAX_N+1)):
        if sos[i] and sos[i-2] and sos[i-6] and sos[i-8]:
            print(i)
            break

Python: primes = [0, 0] + [1]*9999999
for i in range(2, 3163):
    if primes[i]:
        for j in range(i*i, 10000001, i):
            primes[j] = 0
 
while True:
    n = int(input())
    if n == 0:
        break
    for i in range(5, n+1)[::-1]:
        if primes[i] and primes[i-2] and primes[i-6] and primes[i-8]:
            print(i)
            break

Python: from math import sqrt, ceil

N = 10100000
temp = [True]*(N+1)
temp[0] = temp[1] = False
for i in range(2, ceil(sqrt(N+1))):
    if temp[i]:
        temp[i+i::i] = [False]*(len(temp[i+i::i]))

quadruplet = [True, False, True, False, False, False, True, False,True]
while True:
    try: n = int(input())
    except: break
    for i in range(n,9,-1):
        if temp[i] and temp[i-8:i+1] == quadruplet:
            print(i)
            break

Python: primes = [0, 0] + [1]*9999999
for i in range(2, 3163):
    for j in range(i*i, 10000001, i):
        primes[j] = 0

while True:
    n = int(input())
    if n == 0:
        break
    for i in range(5, n+1)[::-1]:
        if primes[i] and primes[i-2] and primes[i-6] and primes[i-8]:
            print(i)
            break

Python: def get_quad(n, p):
    if n < 19:
        return 13
    n = (n + 1) // 10 * 10 - 1
    for ni in range(n,0,-10):
        if p[ni] and p[ni - 2] and p[ni - 6] and p[ni - 8]:
            return ni
        
def sieve():
    n = 10000001
    p = [1] * n
    p[0] = p[1] = 0
    
    for i in range(int(n ** 0.5)):
        if p[i]:
            for j in range(2 * i, len(p), i):
                p[j] = 0
    return p

prime = sieve()
while True:
    n = f.readline().strip()
    if not n.isdigit():
        continue
    n = int(n)
    if n == 0:
        break
    print(get_quad(n, prime))