#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream>
#include <random>
#include<map>
#include <iomanip>
#include <time.h>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
#include <cassert>
#include<fstream>
#include <unordered_map>
#include <cstdlib>
#include <complex>
using namespace std;
#define Ma_PI 3.141592653589793
#define eps 0.00000001
#define LONG_INF 1e18
#define GOLD 1.61803398874989484820458
#define MAX_MOD 1000000007
#define MOD 998244353
#define REP(i,n) for(long long i = 0;i < n;++i)    
#define seg_size 524288
long long gcd(long long a, long long b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}
int is_sosuu[15000000];
int main() {
#define int long long
	long long n;
	cin >> n;
	vector<long long> sosuu;
	for (int i = 2; i <= n; ++i) {
		if (is_sosuu[i] == 0) {
			sosuu.push_back(i);
			for (int q = 2; i*q <= n; ++q) {
				is_sosuu[i * q] = 1;
			}
		}
	}
	long long ans = 0;
	for (int i = (int)sosuu.size() - 1; i >= 0; --i) {
		long long now = sosuu[i] * sosuu[i];
		now -= 2LL;
		if (now >= 0 && now <= n) {
			if (is_sosuu[now] == 0) {
				if (now != 2) {
					ans += 2;
				}
				else {
					ans++;
				}
			}
		}
	}
	cout << ans << endl;
	return 0;
}