def sieve(n):
    is_prime = [True for _ in range(n+1)]
    is_prime[0] = False

    for i in range(2, n+1):
        if is_prime[i-1]:
            j = 2 * i
            while j <= n:
                is_prime[j-1] = False
                j += i
    table = [ i for i in range(1, n+1) if is_prime[i-1]]
    return is_prime, table

N = int(input())
_,table=sieve(N)
DP=[-1]*(N+1)
DP[0]=0
for t in table:
    for i in reversed(range(N)):
        if DP[i]>=0 and i+t<=N:
            DP[i+t] = max(DP[i+t],DP[i]+1)
print(DP[N])