'''
https://yukicoder.me/problems/931
'''

def main():
    import sys
    input = sys.stdin.readline
    sys.setrecursionlimit(10**7)
    from collections import Counter, deque
    #from collections import defaultdict
    from itertools import combinations, permutations, accumulate, groupby
    #from itertools import product
    from bisect import bisect_left,bisect_right
    from heapq import heapify, heappop, heappush
    from math import floor, ceil
    #from operator import itemgetter

    #inf = 10**17
    #mod = 10**9 + 7

    n = int(input())
    def primecheck(n):
        #0~nまで素数判定
        p = [True] * (n + 1)
        p[0] = False
        p[1] = False
        for i in range(2, int(n ** 0.5) + 1):
            if p[i]:
                for j in range(i * i, n + 1, i):
                    p[j] = False
        return p
    
    p = primecheck(n)
    l = []
    for i, x in enumerate(p):
        if x:
            l.append(i)
    
    dp = [-1]*(n+1)
    dp[0] = 0
    for i in l:
        for j in range(n, i-1, -1):
            if dp[j-i] >= 0:
                dp[j] = max(dp[j-i]+1, dp[j])
    print(dp[-1])
            
if __name__ == '__main__':
    main()