#include <fstream>

#define CMAX 2000001

using namespace std;

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

int i, j, n, cnt;
bool ciur[CMAX];

int main()
{

    fin>>n;
    //ciur
    ciur[0] = ciur[1] = 1;
    for(i = 2; i * i <= n; i++)
        for(j = i * i; j <= n ;j += i)
            ciur[j] = 1;
    //afisare nr prime
    for(cnt = 0, i = 1; i <= n; i++)
        cnt += ciur[i];
    fout<<n - cnt;
    return 0;
}