#include <algorithm>
#include <cmath>
#include <complex>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <vector>

using namespace std;

using ll = long long;
using P = pair<int, int>;

const long long MOD = 1e9+7;

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; }

vector<int> sieve(int n) {
    vector<int> is_prime(n + 1, true);
    for (int i = 2; i <= n; i++) {
        if (!is_prime.at(i)) continue;
        
        is_prime.at(i) = true;
        for (int j = i + i; j <= n; j += i) is_prime.at(j) = false;
    }
    vector<int> res;
    for (int i = 2; i <= n; i++) if (is_prime.at(i)) res.push_back(i);
    return res;
}

int main() { 
    int n;
    cin >> n;
    vector<int> primes = sieve(n);
    map<ll, int> is_square_prime;
    for (int p: primes) {
        is_square_prime[(ll)p * p]++;
    }

    int cnt = 0;
    for (int p: primes) {
        cnt += is_square_prime[2 + p];
        if (p != 2) cnt += is_square_prime[2 + p];
    }
    cout << cnt << endl;
}