from collections import defaultdict

n = int(input())

IsPrime = [True for _ in range(n + 1)]
IsPrime[0] = IsPrime[1] = False
Primes = []
for i in range(2, n + 1):
    if IsPrime[i]:
        Primes.append(i)
        for j in range(i * i, n + 1, i):
            IsPrime[j] = False
C = defaultdict(lambda: -1)
C[0] = 0
for p in Primes:
    NC = defaultdict(lambda: -1)
    N = C.keys()
    for i in N:
        NC[i] = max(NC[i], C[i])
        if i + p <= n:
            NC[i + p] = max(NC[i + p], C[i] + 1)
    C = NC
print(C[n])