#include <cmath>
#include <array>
#include <cstdio>
#include <cstdlib>
#include <vector>
#include <algorithm>
using namespace std;

const int N = 5E5;

array<int, N + 1> lp;

vector<int> sieve(const int n) {
    int lim = ceil(sqrt(n));
    lp.fill(-1); lp[0] = lp[1] = 1;
    for (int i = 2; i <= lim; ++i) {
        if (lp[i] == -1) {
            lp[i] = i;
            for (int j = i << 1; j <= n; j += i) {
                if (lp[j] == -1) lp[j] = i;
            };
        };
    };
    for (int i = lim; i <= n; ++i) if (lp[i] == -1) lp[i] = i;
    vector<int> primes;
    for (int i = 2; i <= n; ++i) if (lp[i] == i) primes.emplace_back(i);
    return primes;
}

int main() {
    int n; scanf("%d", &n);
    vector<int> primes = sieve(n); int nprimes = primes.size();
    vector<int> sqrps;
    for (auto it = primes.begin(), end_it = upper_bound(primes.begin(), primes.end(), int(ceil(sqrt(primes.back() << 1)))); it != end_it; ++it) sqrps.emplace_back(*it * *it);
    int res = 0;
    for (const auto &r : sqrps) for (auto i = 0, p = 0, q = 0; i < nprimes && (q = primes[i]) <= n; ++i) {
        p = r - q;
        if (p > 1 && p <= n && lp[p] == p) ++res;
    };
    printf("%d", res);
}