def era(n):
    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
    
    return [i for i in range(n+1) if is_prime[i]]

N = int(input())
primes = era(N)
dp = [-1] * (N+1)

for prime in primes:
    for i in range(N, -1, -1):
        if i-prime >= 0 and dp[i-prime] != -1:
            dp[i] = max(dp[i], dp[i-prime]+1)
    
    dp[prime] = max(dp[prime], 1)
    
print(dp[N])