#include<iostream>
#include<fstream>
using namespace std;
fstream f("ciur.in",ios::in);
fstream g("ciur.out",ios::out);
long long i,j,n,i1,m=3;
bool a[1000000000];

int main()
{
    f>>n;

    for(i=6;i<=n;i+=6)
    {  for(i1=i-1;i1<=i+1;i1+=2)
        if(i1%5!=0&&a[i1]!=1)
    {  a[i1]=1;m++;

       for(j=i1;j<=n;j+=i1*6)
       if(j!=i1)
       a[j]=1;

       if(i1%6==5&&i1<n/i1)
       for(j=i1*i1;j<=n;j+=i1*6)
       a[j]=1;
    }
    }
    g<<m;
    return 0;
}