2
1 31
 2
1 0
 10
450661 128600 993228 725823 293549 33490 843121 903634 556169 448234
 1
1
 5
1 3 5 7 9
 6
524 529 5249 524 529 529
 3
1 2 3
 2
0 1
 55
0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 3 4 5 6 7 8 9 4 5 6 7 8 9 5 6 7 8 9 6 7 8 9 7 8 9 8 9 9
 16
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
 3
128 1024 2048
 10
3 3 3 5 5 3 3 3 3 5
 1
0
 2
1 2
 2
0 0
 2
1 1

0
 2
 632
 0
 0
 24
 2
 2
 621247139
 64594
 4
 0
 1
 1
 3
 0

#include <bits/stdc++.h>
using namespace std;
vector<int> pr;
bool used[123456];
vector<pair<int, int> > otv;
int main() {
  ios_base::sync_with_stdio(0);
  int n;
  cin >> n;
  vector<char> prime(n + 1, true);
  prime[0] = prime[1] = false;
  for (int i = 2; i <= n; ++i)
    if (prime[i])
      if (i * 1ll * i <= n)
        for (int j = i * i; j <= n; j += i) prime[j] = false;
  for (int i = 2; i <= n; i++)
    if (prime[i]) pr.push_back(i);
  for (int i = 0; i < pr.size(); i++) {
    bool ip = 0;
    int x;
    for (int j = pr[i]; j <= n; j += pr[i]) {
      if (!used[j]) {
        if (!ip) {
          ip = 1;
          x = j;
        } else {
          ip = 0;
          used[x] = 1;
          used[j] = 1;
          otv.push_back(make_pair(x, j));
        }
      }
    }
  }
  cout << otv.size() << endl;
  cout << 0;
  return 0;
}
