#include <cstdio>
using namespace std;
unsigned n,i,nrprim,j;
char a[2000005];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    nrprim=1;
    for(i=3;i*i<=n;i+=2)
    {
        if(!a[i])
            nrprim++;
        for(j=i*i;j<=n;j+=2*i)
            a[j]=1;
    }
    for(;i<=n;i++)
        if(!a[i]&&i%2)
            nrprim++;
    printf("%d",nrprim);
    return 0;
}