#include<fstream.h>
#include<iostream.h>
int a,n,i;
char x[250000];
int main()
{ifstream in("ciur.in");
ofstream out("ciur.out");
in>>n;
x[0]=x[0]|(1 << 1);
for(i=2;i<=n;i++)
{
	if((x[i/8]&(1<<(i%8)))==0) {
		for(int j=2*i;j<=n;j+=i) x[j/8]=x[j/8] | (1<< (j%8));
	}
}
for(i=1;i<=n;i++)
	if((x[i/8]&(1<<(i%8)))==0) {

		 a++;
	}
out<<a<<endl;
in.close();
out.close();
return 0;
}