#include <iostream>
#include <cstring>
#include <vector>
#include <set>
#include <list>
#include <map>
#include <deque>
#include <algorithm>
#include <utility>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
#define for1(i,n) for (ll i=0;i<(n);i++)
#define for2(i,m,n) for (ll i=(m);i<(n);i++)
#define for3(i,m,n,d) for (ll i=(m);i<(n);i+=(d))
#define DEBUG 0

void solve()
{
    ll N;
    cin >> N;
    char isPrime[N+1];
    for1(i,N+1) {
        isPrime[i] = 1;
    }
    isPrime[1] = 0;
    for2 (i,2,N+1) {
        if (!isPrime[i]) continue;
        for3(j,i*2,N+1,i) {
            isPrime[j] = 0;
        }
    }
    vector<ll> primes;
    for2 (i,2,N+1) {
        if (isPrime[i]) {
            primes.push_back(i);
        }
    }
    vector<ll> r2(N*2+1,0);
    for (auto p : primes) {
        ll r = p * p;
        if (r <= N*2) {
            r2[r] = 1;
        }
    }

    ll ans = 0;
    for (auto p : primes) {
        ll r = p + 2;
        //cout << p << " " << q << " " << r << endl;
        if (r2[r]) {
            ++ans;
        }
    }
    if (ans == 0) {
        cout << 0 << endl;
    } else {
        cout << ans*2-1 << endl;
    }
}

int main()
{
    do {
        solve();
    } while (DEBUG);
}