#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for(int i = 0; i < (int)n; ++i)
#define FOR(i, a, b) for(int i = a; i < (int)b; ++i)
#define rrep(i, n) for(int i = ((int)n - 1); i >= 0; --i)

typedef long long ll;
typedef long double ld;

const int Inf = 1e9;
const double EPS = 1e-9;
const int MOD = 1e9 + 7;

bool isPrime(int x) {
    if (x == 0 || x == 1) return false;
    for (int i = 2; i * i <= x; ++i) {
        if (x % i == 0) return false;
    }

    return true;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(0);
    int n;
    cin >> n;
    int res = 0;
    vector<ll> prime;
    rep (i, n + 1) {
        if (isPrime(i)) prime.push_back(i);
    } 
    rep (i, prime.size()) {
        ll tmp = prime[i] * prime[i] - 2;
        if (tmp < 2) continue;
        auto x = lower_bound(prime.begin(), prime.end(), tmp);
        if (*x == tmp) {
            res++;
            if (*x != 2) res++;
        }
    }
    cout << res << endl;
    
    return 0;
}