#include <iostream>
#include <vector>

using namespace std;

// エラトステネスの篩  O(nloglogn)
// create p (1<=p<=n and p is a prime nubmer)
#define MAX_N 100000
vector<long long> prime;
bool is_prime[MAX_N + 1];
long long sieve(long long n)
{
  long long p = 0;
  for (long long i = 0; i <= n; i++) is_prime[i] = true;
  is_prime[0] = is_prime[1] = false;
  for (long long i = 2; i <= n; i++) {
    if (!is_prime[i]) continue;
    prime.push_back(i);
    for (long long j = 2 * i; j <= n; j += i) {
      is_prime[j] = false;
    }
  }
  return p;
}

int dp[3000][21000];
int main()
{
  for (int i = 0; i < 3000; i++) {
    for (int j = 0; j < 21000; j++) {
      dp[i][j] = -1;
    }
  }
  int N;
  cin >> N;
  sieve(N);

  dp[0][0] = 0;
  for (int i = 0; i < prime.size(); i++) {
    for (int j = 0; j <= N; j++) {
      if (dp[i][j] < 0) continue;
      dp[i + 1][j] = max(dp[i + 1][j], dp[i][j]);
      if (j + prime[i] >= N) continue;
      dp[i + 1][j + prime[i]] = max(dp[i + 1][j + prime[i]], dp[i][j] + 1);
    }
  }
  cout << dp[prime.size()][N] << endl;

  return 0;
}