#include <stdio.h>
using namespace std;

int main()
{
    FILE *fin,*fout;
    fin=fopen("ciur.in","r");
    fout=fopen("ciur.out","w");
    int i,m,k=0,p=0,x;
    long n,a[50000];
    fscanf(fin,"%ld",&n);
    for(i=2;i<=n;i++)
        a[i]=i;
    m=2;
    do{
        k=k+1;
        for(i=m+1;i<=n;i++)
            if((a[i]%m==0)&&(a[i]!=0))
                {a[i]=0;p=p+1;}
        for(i=m+1;i<=n;i++)
            if(a[i]!=0)
                {
                m=a[i];
                break;
                }
    } while(k<=n-p);
    x=0;
    for(i=2;i<=n;i++)
     if(a[i]!=0)
        x++;
    fprintf(fout,"%d ",x);
    return 0;
}