import numpy as np


def primes_np(n):
    is_prime = np.ones(n + 1, dtype=bool)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, int(n ** 0.5) + 1):
        if not is_prime[i]:
            continue
        is_prime[i * 2:n + 1:i] = False
    return np.where(is_prime)[0].tolist()


N = int(input())
MAX = 10 ** 5
dp = np.full(N + 1, -MAX)
dp[0] = 0
for p in primes_np(N):
    new_dp = dp.copy()
    new_dp[p:] = np.maximum(dp[p:], dp[:-p] + 1)
    dp = new_dp
print(ans if (ans := dp[N]) >= 1 else -1)