import math
N = int(input())


def eratos(n):
    S = []
    isprime = [True] * (n + 1)
    isprime[0] = False
    isprime[1] = False
    for i in range(2, int(math.sqrt(n)) + 1):
        if isprime[i]:
            j = i + i
            while j <= n:
                isprime[j] = False
                j = j + i

    for i in range(n + 1):
        if isprime[i]:
            S.append(i)
    return S


primes = eratos(N)
dp = [[0] + [-1] * N for i in range(len(primes) + 1)]
for i in range(len(primes)):
    for w in range(N + 1):
        if w + primes[i] <= N and dp[i][w] != -1:
            dp[i + 1][w + primes[i]] = dp[i][w] + 1
        dp[i + 1][w] = max(dp[i][w], dp[i + 1][w])
possible_values = (i[N] for i in dp)
print(max(possible_values))