#include <bits/stdc++.h>


using namespace std;
typedef long long ll;
#define REP(i,n) for(int i=0; i<int(n); i++)
#define FOR(i,m,n) for(int i=int(m); i<int(n); i++)
#define ALL(obj) (obj).begin(),(obj).end()
#define VI vector<int>
#define VLL vector<long long>
#define VVI vector<vector<int>>
#define VVLL vector<vector<long long>>
#define VC vector<char>
#define VS vector<string>
#define VVC vector<vector<char>>
#define VB vector<bool>
#define VVB vector<vector<bool>>
#define fore(i,a) for(auto &i:a)

typedef pair <int, int> P;
template<class T> bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
const int  INF = 1 << 30;
const ll INFL = 1LL << 60;
const ll mod = 998244353;

int max_prime = 1000005;

vector<bool> isprime(max_prime, true);

void solve() {
	isprime[0] = false;
	isprime[1] = false;
	isprime[2] = true;

	for (int j = 2; 2*j < max_prime; j++) {
		isprime[2 * j] = false;
	}
	for (int i = 3; i < max_prime; i += 2) {
		if (!isprime[i])continue;
		for (int j = 2; i*j < max_prime; j++) {
			isprime[i*j] = false;
		}
	}
}


int main() {
	
	int n;
	cin >> n;

	ll ans = 0;

	solve();
	for (ll i = 2; i*i - 2 <= n; i++) {
		if (!isprime[i])continue;
		if (isprime[i*i - 2]) {
			if (i == 2) {
				ans++;
			}
			else ans += 2;
		}
	}

	cout << ans << endl;
	

	
}