def primes(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(i * 2, n + 1, i):
            is_prime[j] = False
    return [i for i in range(n + 1) if is_prime[i]]

N = int(input())
l = primes(N)

dp = [ [ 0 for j in range(N+1)]  for i in range(len(l)+1)]
t = 0
for i in range(len(l)):
    t += l[i]
    for j in range(min(N+1,t+1)):
        if j - l[i] >= 0:
            dp[i+1][j] = max(dp[i][j] ,  dp[i][j-l[i]]+ 1)
        else:
            dp[i+1][j] = dp[i][j]


ans = 0
for i in range(len(l)+1):
    ans = max(ans , dp[i][N])
if ans == 0:
    print(-1)
else:
    print(ans)