#include <iostream>
#include <fstream>
int n, i, j;
#define fi for(i=2;i<=n;++i)
#define fj for(j=i+i;j<=n;j+=i)
#define nmax 2000005
bool a[nmax];
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int main()
{
	int  num=0;
	f >> n;
	fi
	    a[i]=1;
	    fi
		if (a[i])
		{
    num++;
    fj
	a[j] = 0;
        }
	g << num << "\n";
	return 0;
}