#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

vector<bool> isprime;

void eratos(ll n) {
	isprime.resize(n + 1);
	for (ll i = 0; i <= n; i++) {
		isprime[i] = true;
	}
	isprime[0] = false;
	isprime[1] = false;
	for (ll i = 2; i * i <= n; i++) {
		if (isprime[i]) {
			ll j = i + i;
			while (j <= n) {
				isprime[j] = false;
				j = j + i;
			}
		}
	}
}

int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	ll N; cin >> N;
	eratos(1000050);
	vector<ll> p;
	for (ll i = 3; i <= N; i++) if (isprime[i]) p.push_back(i);
	vector<bool> h(1005000, false);
	for (ll i = 1; i * i <= 1000000; i++) {
		if(isprime[i]) h[i * i] = true;
	}
	ll res = 0;
	for (ll e : p) {
		if (h[2 + e]) res += 2;
	}
	if (N >= 4) res++;
	cout << res << endl;
	return 0;
}