def seachPrimeNum(N):
    max = int(N ** 0.5)
    seachList = [i for i in range(2, N + 1)]
    primeNum = []
    while seachList[0] <= max:
        primeNum.append(seachList[0])
        tmp = seachList[0]
        seachList = [i for i in seachList if i % tmp != 0]
    primeNum.extend(seachList)
    return primeNum


N = int(input())
if N == 1:
    print(-1)
    exit()
PL = seachPrimeNum(N)
X = [0] * (N+1)
dic = {}
dic[0] = 0
for p in PL:
    dic2 = {}
    for k, v in dic.items():
        if k + p > N:
            continue
        if k + p in dic:
            if dic[k + p] < dic[k] + 1:
                dic2[k + p] = dic[k] + 1
        else:
            dic2[k + p] = dic[k] + 1
    dic.update(dic2)
if N in dic:
    print(dic[N])
else:
    print(-1)