#include <fstream>
using namespace std;
ifstream cin("ciur.in");
ofstream cout("ciur.out");

bool c[2000001];
int x = 2000001;
int p;

void ciur()
{
    c[1]=c[0]=1;
    for(int i = 2 ; i * i <= x ; ++i)
        for(int j = 2 ; i * j <= x ; ++j)
            c[i*j]=1;
}

int main()
{
    int n;
    cin >> n;
    ciur();
    for(int i = 1 ; i <= n ; ++i)
        if(c[i]==0)
            p++;
            cout<<p;
    return 0;
}