#include <bits/stdc++.h>
#define INF 2147483647
#define INF_LL 9223372036854775807
#define MOD 1000000007
using namespace std;
typedef long long int ll;
typedef unsigned long long int ull;

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() {
	eratosthenes p;
	int N, ans = 1;
	cin >> N;
	if (N == 1) {
		cout << 0 << endl;
		return 0;
	}
	for (int i = 1; i < p.prime_n.size() && p.prime_n[i] <= N; i++) {
		int r = 2 + p.prime_n[i], r_ = floor(sqrt(r));
		if (r == r_*r_ && p.prime[r_]) {
			ans += 2;
		}
	}
	cout << ans << endl;
	return 0;
}