#include <cstdio>
#define N 2000000
#include <bitset>
using namespace std;
bitset <N> v;
int nr,n;
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    v[0]=1;v[1]=1;
    for(int i=2;i<<1<=N;i++) v[i<<1]=1;
    for(int i=3;i*i<=N;i+=2)
    {
        for(int i1=i;i*i1<=N;i1+=2) v[i*i1]=1;
    }
    for(int i=2;i<=n;i++) if(v[i]==0) nr++;
    printf("%d",nr);

    return 0;
}