#include <fstream>
using namespace std;
ifstream cin("ciur.in");
ofstream cout("ciur.out");
bool v[2000005];
int main()
{
    ios_base::sync_with_stdio();
    int n,s=1;
    cin>>n;
    v[0]=v[1]=1;
    for(int i=4;i<=n;i+=2)
        v[i]=1;
    for(int i=3;i<=n;i+=2)
        {
        if(v[i]==0)
            for(int j=2*i;j<=n;j+=i)
                v[j]=1;
        s+=1-v[i];
        }
    cout<<s;
    return 0;
}