#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <math.h>
#include <cmath>
#include<cctype>
#include<string>
#include<set>
#include<iomanip>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include<bitset>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
using namespace std;
using ll = long long;
template<typename T>using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;
const ll MOD = 1e9 + 7;
const ll inf = 1LL << 60;
#define all(x) (x).begin(),(x).end()
#define puts(x) cout << x << endl;
#define rep(i,m,n) for(ll i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(ll i = m;i >= n;--i)
#define INF INT_MAX/2


vector<int>pr;
bool prime(ll n) {
	if (n == 1) {
		return false;
	}
	for (ll i = 2; i*i <= n; i++) {
		if (n%i == 0) {
			return false;
		}
	}
	return true;
}
int main() {
	int n;
	cin >> n;

	for (int i = 1; i*i <= 1e6; i++) {
		if (prime(i))pr.pb(i);
	}

	int ans = 0;
	fore(x,pr) {
		if (x > n)break;
		else if (x == 2) {
			ans++;
		}
		else {
			if (prime(x*x - 2) && x*x - 2 <= n) {
				ans += 2;
			}
		}
	}
	cout << ans << endl;

	return 0;
}