from math import sqrt, ceil
import sys
sys.setrecursionlimit(10**7)
from functools import lru_cache
inf = 10 ** 18

@lru_cache(maxsize=None)
def dfs(v, ind):
    ans = -inf
    if v == 0:
        return 0
    for i in range(ind, len(P)):
        if P[i] > v:
            break
        ans = max(ans, dfs(v - P[i], i + 1) + 1)
    return ans


def Sieve(n):
    lst = [True] * (n + 1)
    S = set()
    for i in range(2, ceil(sqrt(n)) + 1):
        if lst[i]:
            for j in range(2 * i, n + 1, i):
                lst[j] = False
    for i in range(2, n + 1):
        if lst[i]:
            S.add(i)
    return sorted(list(S))

N = int(input())
P = Sieve(N + 100)
ans = dfs(N, 0)
print(ans) if ans > 0 else print(-1)