#異なる素数の和

# dp[sum] := num

def showPrimeNum(N):
	""" N以下の素数を返すプログラム """
	is_prime_table = [0] * (N+1) 
	is_prime_table[1] = 0
	prime_list = []

	for i in range(2,N//2+1):
		if is_prime_table[i] == 0:
			j = 2 * i	#イテレータ初期化
			while (j <= N):
				is_prime_table[j] = 1
				j += i 		#掛け算より足し算の方が、計算コストが少なくて良い

	for i in range(1,N+1):
		if is_prime_table[i] == 0:
			prime_list.append(i)

	return prime_list[1:]


if __name__ == "__main__":

	INF = float('inf')

	N = int(input())
	primeNum = showPrimeNum(N)
	l = len(primeNum)

	dp = [-INF] * (N+1)
	dp[0] = 0

	for j in range(0,l):
		for i in range(N,-1,-1):
			if i - primeNum[j] >= 0:
				dp[i] = max([dp[i-primeNum[j]] + 1,dp[i]])

	print(dp[N])