N=int(input())

def list_primes(limit):
    primes = []
    is_prime = [True] * (limit + 1)
    is_prime[0] = False
    is_prime[1] = False

    for p in range (0, limit + 1):
        if not is_prime[p]:
            continue
        primes.append(p)
        for i in range(p*p, limit + 1, p):
            is_prime[i] = False

    return primes

primes=list_primes(N)
dp=[[-10**10]*(N+1) for _ in range(len(primes)+1)]
dp[0][0]=0
for i in range(1,len(primes)+1):
    for j in range(N+1):
        dp[i][j]=max(dp[i][j],dp[i-1][j])
        if j-primes[i-1]>=0:
            dp[i][j]=max(dp[i][j],dp[i-1][j-primes[i-1]]+1)

if dp[len(primes)][N]<0:
    print(-1)
else:
    print(dp[len(primes)][N])