def makePrimes(n: int) -> list:
    sieve = [True] * (n + 1)
    p = 2
    c = 0
    while p * p <= n:
        if sieve[p]:
            for i in range(p * 2, n + 1, p):
                sieve[i] = False
        p += 1
    for i in range(2, n + 1):
        if sieve[i]:
            yield i


def dynamic_knapsack(constrain: int) -> int:
    # dp = [[0 if i == 0 else -1 for i in range(constrain+1)] for j in range(constrain+1)]
    nn = range(constrain + 1)
    dp = [[0] + [-1] * constrain]
    add_dp = dp.append
    primes = makePrimes(constrain)
    i = 0
    for p in primes:
        i += 1
        add_dp([0] + [-1] * constrain)
        for w in nn:
            dp[i][w] = max(1 + dp[i - 1][w - p], dp[i - 1][w]
                           ) if p <= w and dp[i - 1][w - p] != -1 else dp[i - 1][w]
    return dp[i - 1][constrain]


if __name__ == "__main__":
    n = int(input())
    result = dynamic_knapsack(n)
    print(result)