#include <iostream>
#include <fstream>
using namespace std;

char pr[2000001];

int main()
{
    int n,i,j;
    fstream f("ciur.in",ios::in);
    f>>n;
    f.close();
    f.open("ciur.out",ios::out);
    i=2;
    pr[0]=pr[1]=1;
    while(i<=n)
    {
        j=2;
        while(i*j<=n)
        {
            pr[i*j]=1;
            j++;
        }
        i++;
        while(i<=n&&pr[i])i++;
    }
    int s=0;
    for(i=0;i<=n;i++)
        s+=1-pr[i];
    f<<s;
    return 0;
}