#include <fstream>
#include <bitset>
using namespace std;

int main() {
	ifstream fin("ciur.in");
	ofstream fout("ciur.out");
	int n; fin >> n;
	bitset<2000001> sieve;
	for (int i=3,j; i<=n; ) {
		j=i*i;
		if (j<0) break;
		for (; j<=n; j+=(i<<1)) {
			sieve.set(j);
		}
		while ((i+=2)<=n && sieve[i]);
	}
	fout << n-n/2-sieve.count();//1 counted,2 not counted
	return 0;
}