#include<cstdio>
int n,i,j,k=1,p[2000005];
int main()
{freopen("ciur.in","r",stdin);
freopen("ciur.out","w",stdout);
scanf("%d",&n);
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[j>>3]|=(1<<(j&7));
for(i=1;2*i+1<=n;i++) 
if((p[i>>3]&(1<<(i&7)))==0)
   k++;
printf("%d",k);
return 0;}