#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];
cin>>n;
for(i=2;i<=n;i++)
{
    if(v[i]==0)
    { nr++;
        k=i*2;
        while(k<=n)
        {
            for(j=3;k<=n;j++)
            {v[k]++;
                k=i*j;

            }
        }
    }
}
cout<<nr;
    return 0;
}