#include<fstream>

#include<bitset>

using namespace std;

ifstream cin("ciur.in");

ofstream cout("ciur.out");

#define M 2000005

bitset <M> bitsett;



int main(){

    int n, cnt=1;

    cin>>n;

    for(int i=2; i*i<=n; ++i)

        if(!bitsett[i]){

            for(int j=i+i; j<=n; j+=i)

                bitsett[j]=1;

        }

    for(int i=3; i<=n; i+=2)

        if(!bitsett[i])

            cnt++;

    cout<<cnt;

    return 0;

}