#include <iostream>
#include <fstream>

using namespace std;

ifstream in("ciur.in");
ofstream out("ciur.out");

int main()
{ unsigned long long n,nr=0,i,k,j;
bool v[2000010];
in>>n;
for(i=2;i<=n;i++)
{
    if(v[i]==0)
    { nr++;
        k=i;
        while(k<=n)
        {
            for(j=2;k<=n;j++)
            {
                k=i*j;
                if(!k<=n)
                    break;
                v[k]++;
            }
        }
    }
}
out<<nr;
    return 0;
}