/* */
#include<stdio.h>
#include<stdlib.h>
char *v;
int n,nr=1;
int main()
{register int i,j;
    freopen("ciur.in","rt",stdin);
    freopen("ciur.out","wt",stdout);
    scanf("%d",&n);
    v=(char*)calloc(n/2/8+1,sizeof(char));
    for(i=1;((i*i)<<1)+(i<<1)<=n;++i)
       if((v[i>>3]&(1<<(i&7)))==0)
       for(j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1) v[j>>3]|=(1<<(j&7));
    for(i=1;2*i+1<=n;++i)
       if((v[i>>3]&(1<<(i&7)))==0) ++nr;
    printf("%d",nr);
    free(v);
    return 0;
}