#include <algorithm>
#include <iostream>
#include <vector>
#include <string>
#include <climits> // FOO_MAX, FOO_MIN
#include <cmath> 
#include <cstdlib> // abs(int)
#include <numeric>

#define roundup(n,d) ( ((n) + ((d)-1)) / (d) )
#define ll long long
#define assign_max(into, compared) (into = max((into), (compared)))
#define assign_min(into, compared) (into = min((into), (compared)))

using namespace std;

bool is_prime(int n){
    if (n <= 1) return false;
    if (n == 2) return true;
    if (n % 2 == 0) return false;
    const int limit = min((int)sqrt(n)+1,n);
    for(int i = 3;i <= limit;i+=2){
        if (n % i == 0){
            return false;
        }
    }
    return true;
}
//[2,limit]
vector<int> primenumbers(int limit){
    vector<int> primes;
    for(int i = 2;i <= limit;i++){
        if(is_prime(i)){
            primes.push_back(i);
        }
    }
    return primes;
}


int main(void){
    int n;
    cin >> n;
    auto primes = primenumbers(n);
    const int primes_n = primes.size();
    vector<vector<int>> dp (primes_n, vector<int> (n+1));
    for(int i = 0;i < primes_n;i++){
        
    }
    cout << primes.size() << endl;
}