#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<utility>
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<functional>
#include<math.h>
#include<random>
#include <bitset>
using namespace std;
#define N (1000000000+7)
//#define N 998244353
#define INF 1e16
typedef long long ll;
typedef pair<int,int> P;
typedef pair<int,P> Q;
 
const int inf = (int)1e9; 
 
ll gcd(ll a, ll b) {
	if (b > a) {
		ll tmp = b;
		b = a;
		a = tmp;
	}
	if (a%b == 0)return b;
	else return gcd(b, a%b);
}

bool prime[1000010];
void furui() {
	int i = 2;
	while (i <= 1000000) {
		int j = 2;
		while (j*j <= i && !prime[i]) {
			if (i%j == 0) {
				prime[i] = true;
				break;
			}
			else j++;
		}
		int z = 2;
		while (!prime[i]) {
			if (i*z <= 1000000) {
				prime[i*z] = true;
				z++;
			}
			else break;
		}
		i++;
	}
}

int main(void){
	furui();
	int n;
	cin>>n;
	ll ans = 0;
	vector<ll>p;
	for(ll i=2;i<=n;i++){
		if(!prime[i]){
			p.push_back(i);
		}
	}
	for(int i=0;i<p.size();i++){
		ll x = p[i]*p[i]-2;
		if(p[i]==2)continue;
		if(x<=0)continue;
		if(x<=n && !prime[x]){
			ans++;
		} 
	}
	if(n==1)cout<<0<<endl;
	else {
		cout<<2*ans+1<<endl;
	}
	return 0;

}