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