#include <bits/stdc++.h>

using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
const int nmax=2000001;
///Complexitate O(n*log(logN))
bitset<nmax>v;
int main()
{
    int n;
    fin>>n;
    v[1]=1;
    for(int i=4;i<=n;i+=2)
        v[i]=1;
    for(int i=3;i*i<=n;i+=2)
        if(v[i]==0)
            for(int j=i*i;j<=n;j+=2*i)
                v[j]=1;
    fout<<n-v.count()<<"\n";
    fin.close();
    fout.close();
    return 0;
}