N = int(input())
is_prime = [1 for _ in range(N+1)]
is_prime[0] = 0; is_prime[1] = 0
for i in range(2, N+1):
    if not is_prime[i]: continue
    for j in range(i*2, N+1, i): is_prime[j] = 0

primes = [i for i in range(len(is_prime)) if is_prime[i]]
C = len(primes)

dp = [[-1] * (N+1) for _ in range(C+1)]
for i in range(0, C+1):
    dp[i][0] = 0

for i in range(C-1, -1, -1):
    for w in range(0, N+1):
        if w - primes[i] < 0: continue
        if dp[i+1][w-primes[i]] != -1:
            dp[i][w] = max(
                dp[i+1][w-primes[i]] + 1,
                dp[i+1][w]
            )
        else:
            dp[i][w] = dp[i+1][w]
print(dp[0][N])