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))