#include <stdio.h>
#include <string.h>

#define dim 125005

char p[dim];
int i,j,N,size;

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));

    size=1;
    for(i=1;((i<<1)+1)<=N;i++)
	if((p[i>>3]&(1<<(i&7)))==0)
            size++;

    printf("%d\n",size);
    
    return 0;
}