from functools import reduce

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

n = int(input())
p = primes(n)
mp = {0:0}
dp = [[-1 for i in range(n+1)] for j in range(2)]
dp[0][0] = 0
ans = -1
for i in range(len(p)):
    for j in range(n+1):
        dp[(i+1)%2][j] = max(dp[i%2][j],dp[i%2][j-p[i]]+1 if j >= p[i] and dp[i%2][j-p[i]] >= 0 else -1)
    ans = max(ans,dp[(i+1)%2][n])
print(ans)