#include <cstdio>
using namespace std;
int n,i,nr,j;
char p[2000010/2/8+1];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    nr=1;
    for(i=1;((i*i)<<1)+(i<<1)<=n;i++)
    {
        if((p[i>>3]&(1<<(i&7)))==0)
        for(j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1)
        p[i>>3]|=(1<<(i&7));
    }
    for(i=1;(i<<1)+1<=n;i++)
    if((p[i>>3]&(1<<(i&7)))==0)
    nr++;
    printf("%d",nr);
    return 0;
}