#include <bits/stdc++.h>
#define nmax 2000005
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bitset<nmax>a;
int n;
void Ciur()
{
    int i,j;
    a[1]=1;
    for(i=4;i<=nmax;i=i+2)
        a[i]=1;
    for(i=3;i*i<=nmax;i=i+2)
        if(a[i]==0)
     for(j=i*i;j<=nmax;j=j+2*i)
        a[j]=1;

}
int main()
{
    int sol=0,i;
    fin>>n;
    Ciur();
    for(i=1;i<=n;i++)
        if(a[i]==0)
        sol++;
    fout<<sol<<"\n";
    fin.close();
    fout.close();
    return 0;
}