#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
FILE*fin=fopen("ciur.in","r");
FILE*fout=fopen("ciur.out","w");
int i,j,k,m,l,n,a,rasp;
//vector <int> v;
char v[5000000];
int main()
{
    fscanf(fin,"%d",&n);
    for (i=1;(i<<1)+1<n;i++)
    if (v[i]==0)
    for(j=(i<<2)-i+1;(j<<1)+1<n;j+=(i<<1)+1)
    v[j]=1;
    for (i=1;(i<<1)+1<n;i++)
    if (v[i]==0)
    ++rasp;
    ++rasp;
    fprintf(fout,"%d\n",rasp);
    return 0;
}