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#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define int ll
using PII = pair<int, int>;
template <typename T> using V = vector<T>;
template <typename T> using VV = vector<V<T>>;
template <typename T> using VVV = vector<VV<T>>;

#define FOR(i, a, n) for (ll i = (ll)a; i < (ll)n; ++i)
#define REP(i, n) FOR(i, 0, n)
#define ALL(x) x.begin(), x.end()
#define PB push_back

const ll INF = (1LL<<60);
const int MOD = 1000000007;

template <typename T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <typename T> T &chmax(T &a, const T &b) { return a = max(a, b); }
template <typename T> bool IN(T a, T b, T x) { return a<=x&&x<b; }
template<typename T> T ceil(T a, T b) { return a/b + !!(a%b); }
template<class S,class T>
ostream &operator <<(ostream& out,const pair<S,T>& a){
  out<<'('<<a.first<<','<<a.second<<')';
  return out;
}
template<class T>
ostream &operator <<(ostream& out,const vector<T>& a){
  out<<'[';
  REP(i, a.size()) {out<<a[i];if(i!=a.size()-1)out<<',';}
  out<<']';
  return out;
}

int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};

//素数ならtrue
bool prime[10000010];
signed main(void)
{
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n;
  cin >> n;

  memset(prime, true, sizeof(prime));
  int cnt = 0;
  prime[0] = prime[1] = false;
  for (int i = 2; i <= 10000000; i++) {
    if (prime[i]) {
      cnt++;
      for (int j = 2 * i; j <= 10000000; j += i) {
        prime[j] = false;
      }
    }
  }

  int ret = 0;
  FOR(i, 3, n+1) {
    if(prime[i] && prime[i+2]) {
      // cout << i << " " << i+2 << endl;
      ret += 2;
    }
  }
  cout << ret << endl;

  return 0;
}