#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <string>
#include <sstream>
#include <complex>
#include <vector>
#include <list>
#include <queue>
#include <deque>
#include <stack>
#include <map>
#include <set>

#define rep(i, n) for (int i = 0; i < (n); i++)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; i--)
#define reps(i, n) for (int i = 1; i <= (n); i++)
#define repi(i, a, b) for (int i = (a); i < (b); i++)
#define all(a) (a).begin(), (a).end()
#define bit(b) (1ull << (b))

using namespace std;
using i32 = long long;
using u32 = unsigned long long;
using i64 = long long;
using u64 = unsigned long long;
using f64 = double;
using vi32 = vector<i32>;
using vu32 = vector<u32>;
using vi64 = vector<i64>;
using vu64 = vector<u64>;
using vf64 = vector<f64>;
using vstr = vector<string>;
using vvi32 = vector<vi32>;
using vvu32 = vector<vu32>;
using vvi64 = vector<vi64>;
using vvu64 = vector<vu64>;
using vvf64 = vector<vf64>;

template<typename T, typename S> void amax(T &x, S y) { if (x < y) x = y; }
template<typename T, typename S> void amin(T &x, S y) { if (y < x) x = y; }

i64 dp[20010];

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(16);
  vi32 primes;
  for (int i = 2; i <= 20000; i++) {
    bool flag = true;
    for (int j = 2; j * j <= i; j++) {
      if (i % j == 0) flag = false;
    }
    if (flag) primes.push_back(i);
  }
  int n;
  cin >> n;
  rep(i, 20010) dp[i] = -1e9;
  dp[0] = 0;
  rep(j, primes.size()) {
    rrep(i, 20000) {
      if (i + primes[j] > 20000) continue;
      if (dp[i] < 0) continue;
      amax(dp[i + primes[j]], dp[i] + 1);
    }
  }
  if (dp[n] < 0) cout << -1 << endl;
  else cout << dp[n] << endl;
  return 0;
}