def make_prime_numbers(n):
    '''
    n以下の素数を列挙したリストを出力する
    計算量：O(NloglogN)
    入出力例：30 -> [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
    '''

    is_prime = [True]*(n+1)
    is_prime[0] = False
    is_prime[1] = False
    for i in range(2, int(n**0.5) + 1):
        if not is_prime[i]:
            continue
        for j in range(2 * i, n + 1, i):
            is_prime[j] = False
    prime_numbers = [i for i in range(n + 1) if is_prime[i]]
    return prime_numbers

n = int(input())
prime_list = make_prime_numbers(n)
# dp[i][j] := i個めまでの素数を選んだときに値がjになるとき選んだ個数の最大値

dp = [[-1]*(n+1) for i in range(len(prime_list) + 1)]

for i in range(len(prime_list)):
    dp[i][0] = 0
for i in range(len(prime_list)):
    for j in range(n+1):
        if prime_list[i] > j:
            dp[i+1][j] = dp[i][j]
        else:
            if dp[i][j-prime_list[i]] == -1:
                dp[i+1][j] = max(dp[i][j], -1)
            else:
                dp[i+1][j] = max(dp[i][j], dp[i][j-prime_list[i]] + 1)
print(dp[len(prime_list)][n])