#include <cstdio>
#include <cmath>
#include <bitset>
using namespace std;
const int NMAX=2000005;
bitset<NMAX> p;
int atkin(int n)
{
    int limit=ceil(sqrt(n>>2)),secventa[]={2,4},index,k1,k,i,j,i2,nr=1;
    for(i=1;i<limit;++i)
    {
        index=0;
        k1=(i*i)<<2;
        j=1;
        if(!(i%3))
        {
            while(1)
            {
                k=k1+j*j;
                if(k>n) break;
                p[k]=~p[k];
                j+=*(secventa+(++index&1));
            }
        }
        else
        {
            while(1)
            {
                k=k1+j*j;
                if(k>n) break;
                p[k]=~p[k];
                j+=2;
            }
        }
    }
    limit=ceil(sqrt(n/3));
    for(i=1;i<limit;i+=2)
    {
        index=1;
        k1=3*i*i;
        j=2;
        while(1)
        {
            k=k1+j*j;
            if(k>n) break;
            p[k]=~p[k];
            j+=*(secventa+(++index&1));
        }
    }
    limit=ceil(sqrt(n));
    for(i=1;i<limit;++i)
    {
        k1=3*i*i;
        if(!(i&1)) j=1,index=0;
        else j=2,index=1;
        while(j<i)
        {
            k=k1-j*j;
            if(k<n) p[k]=~p[k];
            j+=*(secventa+(++index&1));
        }
    }
    p[2]=p[3]=1;
    for(i=5;i<=limit;++i)
    {
        if(p[i])
        {
            i2=i*i;
            for(j=i2;j<=n;j+=i2) p[j]=0;
        }
    }
    for(i=3;i<=n;i+=2)
    {
        if(p[i]) ++nr;
    }
    return nr;
}
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    int n;
    scanf("%d",&n);
    printf("%d\n",atkin(n));
    fclose(stdin);
    fclose(stdout);
    return 0;
}