#include <bits/stdc++.h>
using namespace std;

bool isprime(int n)
{
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

int main()
{
    int n, p = 0;
    cin >> n;
    if (n < 2) {
        cout << 0 << endl;
        return 0;
    }
    for (int r = 2; r * r - 2 <= n; r++) {
        if (isprime(r) && isprime(r * r - 2)) p++;
    }
    cout << 2 * p - 1 << endl;
}