//bestbestbestbestbest17701
#include <bits/stdc++.h>
const int best = 1e6+5;
using namespace std;
long long n,d=0,N;
bool prime[best];

void sieve(){
    for(int i = 0; i <= best;++i) {
        prime[i] = true;
    }
    prime[0] = false;
    prime[1] = false;
    for(int i = 2; i * i <= best; ++i) {
         if(prime[i] == true) {
             for(int j = i * i; j <= best; j += i)
                 prime[j] = false;
        }
    }
}
int main(){
    ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
    freopen("BEAUNUM.inp","r",stdin);
    freopen("BEAUNUM.out","w",stdout);
    cin >> n;
    sieve();
    d = 0;
    N = sqrt(sqrt(n));
    for(int i=2;i<=N;i++)if (prime[i]) ++d;
    cout << d;
    return 0;
}