#include <iostream>
#include<fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
bool ciur[2000005];
int n,i,j,nr;
int main()
{
    in>>n;
    ciur[0] = ciur[1] = 1;
    for(i=4;i<=2000005;i+=2) ciur[i] = 1;
    for(i=3;i*i<=2000005;i+=2)
        for(j=i;j*i<=2000005;j+=2)
            ciur[i*j] = 1;
    for(i=1;i<=n;i++)
        if(ciur[i]==0) ++nr;
    out<<nr;
    return 0;
}