#include <fstream>

using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
char a[2000050];
unsigned i,j,n,nr;
int main()
{
    fin>>n;
    nr++;
    for(i=3;i*i<=n;i+=2)
    {
        if(!a[i])
            nr++;
        for(j=i*i;j<=n;j+=2*i)
            a[j]=1;
    }
    for(;i<=n;i++)
        if(!a[i]&&i%2)
            nr++;
    fout<<(int)nr;
    return 0;
}