#include "bits/stdc++.h"
#define REP(i, n, N) for(ll i = n; i < (N); i++)
#define p(s) cout << (s) << endl
#define p2(a, b) cout << (a) <<" "<< (b) << endl
using namespace std;
typedef long long ll;
ll mod = 1e9+7;
ll inf = 1e18;
vector<ll> hurui_v(ll n) {
    vector<ll> v;
    bool *isPrime_v;
    isPrime_v = new bool[n + 1]; // 処理用のメモリ確保

    // 初期化
    isPrime_v[0] = isPrime_v[1] = false;
    for (ll i = 2; i < n + 1; i++) isPrime_v[i] = true;

    // isPrime[0~n]で素数のものだけtrueにする
    for (ll i = 2; i*i <= n; i++) {
        for (ll j = i * 2; j < n + 1; j += i) {
            isPrime_v[j] = false;
        }
    }

    // 素数のみ追加
    for (ll i = 0; i < n + 1; i++) {
        if (isPrime_v[i]) v.push_back(i);
    }

    delete[] isPrime_v; //メモリ解放
    return v;
}
bool isPrime[500050];
void hurui(ll n) {
    // 初期化
    isPrime[0] = isPrime[1] = false;
    for (ll i = 2; i < n + 1; i++) isPrime[i] = true;

    for (ll i = 2; i*i <= n; i++) {  // iがsqrt(n)となるまで繰り返す
        for (ll j = i * 2; j < n + 1; j += i) {
            isPrime[j] = false;       // 素数でない
        }
    }
    return;
}
int main() {
   ll N, ans;
   ans = 0;
   cin >> N;
   hurui(500010);
    vector<ll> vp = hurui_v(N);
    for(ll i=0; i < vp.size(); i++){
        for(ll k=i; (vp[k]*vp[k] <= 2*N) && k<vp.size(); k++){
            ll j = (vp[k]*vp[k]) - vp[i];
            if(j > N) break;
            if(isPrime[j]){
                ans++;
                if(vp[i]!=j) ans++;
            }
        }
    }
    p(ans);
    return 0;
}