#include <bits/stdc++.h>
#define rep(i, n) for(long long i = 0; i < (long long)(n); i++)
using namespace std;
using ll = long long;


class eratosthenes {
public:
	vector<int> prime_n;
	bool prime[500001];

	eratosthenes() {
		fill(prime, prime + 500001, true); //素数
		prime[0] = prime[1] = false;
		for (int i = 2; i < 500001; i++) {
			if (prime[i] == true) {
				prime_n.push_back(i);
				for (int j = 2; i * j < 500001; j++) {
					prime[i * j] = false;
				}
			}
		}
	}
};

int main(){
    ll n;
    cin >> n;
    eratosthenes p;

    vector<bool> isPrime(500001);
    rep(i, p.prime_n.size()){
        isPrime[p.prime_n[i]] = true;
    } 
    
    int ans = 0;

    rep(i, p.prime_n.size()){
        int q = p.prime_n[i] * p.prime_n[i] - 2;
        if(q > n) break;
        if(isPrime[q]){
            if(q != 2) ans++;
            ans++;
        }
    }

    cout << ans << endl;
    return 0;
}