# https://yukicoder.me/problems/931
import math
N = int(input())


def generate_prime(X):
    max_cand = math.ceil(math.sqrt(X))
    cand_list = range(2, X + 1)
    prime_list = []
    while True:
        prime = cand_list[0]
        prime_list.append(prime)
        cand_list = [i for i in cand_list if i % prime != 0]

        if prime > max_cand:
            prime_list.extend(cand_list)
            break
    return prime_list

prime_list = generate_prime(N)
dp = [[-1 for i in range(N + 1)] for j in range(len(prime_list) + 1)]
dp[0][0] = 0
for i in range(len(prime_list)):
    flag = 0
    dp[i + 1] = dp[i][:]
    for j in range(0, N + 1):
        if dp[i][j] != -1 and j + prime_list[i] <= N:
            dp[i + 1][j + prime_list[i]
                      ] = max(dp[i][j + prime_list[i]], dp[i][j] + 1)

print(dp[-1][N])
# print(dp)