#include <fstream>
#include <cmath>

using namespace std;

ifstream in("ciur.in");
ofstream out("ciur.out");

bool v[2000014];

int main()
{
    int i, n, s=1, j;
    in>>n;
    v[1]=1;
    v[0]=1;
    for(i=4; i<=n; i=i+2)
        v[i]=1;
    for(i=3; i<=n; i=i+2)
        if(!v[i])
        {
            for(int j=2*i; j<=n; j=j+i)
                v[i]=1;
            s++;
        }
    out<<s;
    return 0;
}