N = int(input())

def prime(x):
    prime = [x if x%2==1 else 2 for x in range(x+1)]
    prime[0] = 1

    for i in range(3, int(x**0.5)+2, 2):
        if prime[i] != i:
            continue   
        for j in range(2*i, x+1, i):
            if prime[j] == j:
                prime[j] = i

    p = [i for i in range(2, x+1) if prime[i] == i]
    return p

P = prime(N)
dp = [-1] * (N+1)
dp[0] = 0
for p in P:
    for i in range(N, -1, -1):
        if i + p <= N and dp[i] != -1:
            dp[i+p] = max(dp[i+p], dp[i] + 1)
ans = dp[N]
print(ans)