#include "bits/stdc++.h"

using namespace std;
using ll = long long;
const double pi = acos(-1);
#define FOR(i,a,b) for (ll i=(a),__last_##i=(b);i<__last_##i;i++)
#define RFOR(i,a,b) for (ll i=(b)-1,__last_##i=(a);i>=__last_##i;i--)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define __GET_MACRO3(_1, _2, _3, NAME, ...) NAME
#define rep(...) __GET_MACRO3(__VA_ARGS__, FOR, REP)(__VA_ARGS__)
#define rrep(...) __GET_MACRO3(__VA_ARGS__, RFOR, RREP)(__VA_ARGS__)
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) {
	REP(i, v.size()) { if (i)os << " "; os << v[i]; }return os;
}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v) {
	REP(i, v.size()) { if (i)os << endl; os << v[i]; }return os;
}

const ll INF = 1LL << 60;
ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

#define int long long

inline void my_io() {

	std::ios::sync_with_stdio(false);

	std::cin.tie(0);

	cout << fixed << setprecision(16);

	//cout << setprecision(10) << scientific << ans << endl;
}

//エラトステネスの篩
const ll MAX_N = 500000;
vector<ll> prime;	//i番目の素数
bool is_prime[MAX_N + 1];	//is_prime[i]がtrueならばiは素数

							//n以下の素数の数を返す
ll sieve(ll n) {
	ll p = 0;
	REP(i, n + 1) {
		is_prime[i] = true;
	}
	is_prime[0] = is_prime[1] = false;
	FOR(i, 2, n + 1) {
		if (is_prime[i]) {
			p++;
			prime.push_back(i);
			for (int j = 2 * i; j <= n; j += i) {
				is_prime[j] = false;
			}
		}
	}
	return p;
}

signed main() {
	ll n;

	cin >> n;

	if (n < 2) {
		cout << 0 << endl;
		return 0;
	}

	sieve(n);

	ll ma = prime[prime.size() - 1] + 2;
	ll ans = 1;
	ll num;

	FOR(i, 1, prime.size()) {
		num = prime[i] * prime[i];

		if (num > ma) {
			break;
		}

		if (is_prime[num - 2]) {
			ans += 2;
		}
	}

	cout << ans << endl;
}