#region Header
#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
from queue import PriorityQueue
import bisect
import heapq

def input():
    return sys.stdin.readline()[:-1]

sys.setrecursionlimit(1000000)
#endregion

# _INPUT = """3344
# """
# sys.stdin = io.StringIO(_INPUT)

def get_primes(N):
    a = [True] * (N + 1)
    l = []
    for n in range(2, N + 1):
        if a[n]:
            l.append(n)
            for i in range(n+n, N + 1, n):
                a[i] = False
    return l

def main():
    N = int(input())
    primes = get_primes(N)

    T = [0 for _ in range(N+1)]
    for p in primes:
        T[p] = max(T[p], 1)
        for i in reversed(range(2, N+1)):
            if i == p and T[i] == 1:
                continue
            if T[i] > 0 and i+p <= N:
                T[i+p] = max(T[i+p], T[i] + 1)

    if T[N] > 0:
        print(T[N])
    else:
        print(-1)

if __name__ == '__main__':
    main()