import sys; input = sys.stdin.buffer.readline sys.setrecursionlimit(10**7) from collections import defaultdict con = 10 ** 9 + 7; INF = float("inf") def getlist(): return list(map(int, input().split())) num = 2 * 10 ** 4 + 1 #適当に値を入れる L = [1 for i in range(num)]; L[0] = 0; L[1] = 0 plist = [] for i in range(num): if L[i] == 1: plist.append(i); c = 2 while i * c <= num - 1: L[i * c] = 0; c += 1 #処理内容 def main(): N = int(input()) DP = [0] * (N + 1) DP[0] = 1 for i in plist: for j in range(N, -1, -1): if j + i <= N and DP[j] != 0: DP[i + j] = max(DP[i + j], DP[j] + 1) # print(DP) if DP[N] == 0: print(-1) else: print(DP[N] - 1) if __name__ == '__main__': main()