#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rep3(i, l, n) for (int i = l; i < n; ++i)
#define chmax(a, b) a = max(a, b)
#define chmin(a, b) a = min(a, b)
#define out(a) cout << a << endl
#define SZ(v) (int)v.size()

vector<int> sieve() {
    const int MAX_N = 7369791 + 1;
    vector<int> v(MAX_N, 0);
    v[0] = v[1] = 1;
    for (int i = 2; i * i <= MAX_N; ++i) {
        int tmp = 2;
        while (tmp * i <= MAX_N) {
            v[tmp++ * i] = 1;
        }
    }
    return v;
}

int main() {
    int n; cin >> n;
    vector<int> v = sieve();
    int cnt = 0;
    //1つを2に固定
    rep3(r, 2, n + 1) {
        if (v[r] == 1) continue;
        if ((ll)r * r - 2 > n) break;
        int p = r * r - 2;
        if (v[p] == 1) continue;
        //out(2 << " " << p << " " << r);
        if (p == 2) cnt++;
        else cnt += 2;
    }
    out(cnt);
}