01.# include <fstream>
02.#define N 2000001
03.using namespace std;
04.char c[N];
05.long long n;
06.void ciur()
07.{
08.int d=2;
09.while (d*d<=n)
10.{
11.if (!c[d])
12.for (int i=d*d; i<=n; i+=d)
13.c[i]=1;++d;
14.}
15.long long num=0;
16.for (int i=2; i<=n; ++i)
17.if (!c[i]) num++;
18.ofstream g("ciur.out");
19.g<<num;
20.g.close();
21.}
22.void citire()
23.{
24.ifstream f("ciur.in");
25.f>>n;
26.f.close();
27.}
28.int main()
29.{
30.citire();
31.ciur();
32.return 0;
33.}