#include <iostream>
#include <string>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>


using namespace std;

#define REP(i, n) for(ll i = 0;i < n;i++)
#define REPR(i, n) for(ll i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define FORR(i, m, n) for(ll i = m;i >= n;i--)
#define REPO(i, n) for(ll i = 1;i <= n;i++)
#define ll long long
#define INF (ll)1 << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(),n.end()
#define MOD (ll)1000000007
#define P pair<ll, ll>

ll n, ans = 0;
bool IsPrime(ll n) {
	if (n <= 1)return false;
	for (ll i = 2; i <= sqrt(n); i++)
	{
		if (n % i == 0)return false;
	}
	return true;
}
int main() {
	cin >> n;
	for (int i = 2; i * i <= n + 1000; i++){
		if (IsPrime(i)) {
			if (IsPrime(i * i - 2) and i * i - 2 <= n) {
				if (i == 2)ans--;
				ans += 2;
			}
		}
	}
	cout << ans << endl;
}