#include <iostream>
#include <fstream>
using namespace std;
int v[2000001],i,j,p,K,n;
int main()
ifstream in("ciur.in");
ofstream out("ciur.out");
{in>>n;
for(i=2;i<=n;i++){
    K=0;
for(p=2;p<=i/2;p++)
    if(i%p==0)
    K++;
if(K!=0)
    v[i]=1;
    else
    {v[i]=0;
    for(j=2*i;j<=n;j++)
        v[j]=1;
    }
}
p=0;
for(i=2;i<=n;i++)
    if(v[i]==0)
    p++;

    out<<p;

    return 0;
}