#include <iostream>
#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
bool v[2000001];
int main()
{
    long long n;
    int i,j,m,c=2,cnt=0;
    in>>n;
    for(i=2;i<=n;i++){
        for(j=2;j*j<=i;j++){
            if(i%j==0)
            c++;}
        if(c==2)
            for(m=2*i;m<=n;m=m+i)
            v[m]=1;
    }
    for(i=2;i<=n;i++)
        if(v[i]==0)
        cnt++;
        out<<cnt;
    return 0;
}