#include <bits/stdc++.h>
using namespace std;

long long n,a,b,ans=0;
int x[50001];

void sieve(int N) {
    for(int i=0;i<=N;++i)x[i]=1;
    x[0]=0;
    x[1]=0;
    for(int i=2;i*i<=N;++i)
        if(x[i]==1) for(int j=i*i;j<=N;j+=i)x[j]=0;
}
int main()
{
    freopen("BEAUNUM.inp","r",stdin);
    freopen("BEAUNUM.out","w",stdout);
    sieve(35000);
    cin>>n;
    for(int i=1;i<=(int)sqrt(sqrt(n));i++)ans+=x[i];
    cout<<ans;
}