n = int(input())
num = []
table = [True] * (n + 1)

for i in range(2, n + 1):
    if not table[i]:
        continue
    k = i + i
    while k < n + 1:
        table[k] = False
        k += i

    num.append(i)

dp = [-1] * 20001
dp[0] = 0

for prime in num:
	for i in range(n, 0, -1):
		if i - prime >= 0:
			if dp[i - prime] >= 0:
				dp[i] = max(dp[i], dp[i - prime] + 1)
print(dp[n])