import random


M = 1000
ps = set(primes(3, M+1))
#random.shuffle(ps) #järjestys voi muuttaa tulosta

toGet = set(range(6, M+2, 2))

a = []

def getBestPrime():
    bestP = None
    bestVal = 0
    for p in ps:
        v = sum(1 for x in a+[p] if x+p in toGet)
        if bestP==None or v>bestVal:
            bestVal = v
            bestP = p
    return bestP


while len(toGet):
    p = getBestPrime()
    ps.remove(p)
    a.append(p)
    for x in a:
        if x+p in toGet: toGet.remove(x+p)

print (len(a))
print (sorted(a))