#include <bits/stdc++.h>
#define rep(i,n) for(int i=(0);i<(n);i++)

using namespace std;

typedef long long ll;

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);

	ll n;
	cin >> n;

	if(n == 1){
		cout << 0 << endl;
		exit(0);
	}

	int max_n = 505050;
	vector<bool> isprime(max_n, true);
	vector<ll> primes;
	isprime[0] = isprime[1] = false;
	for(int i = 2; i < max_n; i++){
		if(isprime[i]){
			primes.push_back(i);
			for(int j = 2 * i; j < max_n; j += i) isprime[j] = false;
		}
	}

	set<ll> psq;
	for(ll p : primes){
		if(p > n) break;
		psq.insert(p * p);
	}

	// (2, 2, 2)
	ll ans = 1;
	for(ll p : primes){
		if(p == 2) continue;
		if(p > n) break;
		if(psq.count(p + 2) == 1) ans += 2;
 	}
	
	cout << ans << endl;

}