#include<fstream.h>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int n,x,nr,v[2000001];
int prim(int x)
	{for(int d=2;d<x/2;d++)if(x%d==0)return 0;
	return 1;
	}
int main()
	{f>>n;
	while(x*6<n){if(prim(x*6-1))nr++;
				if(prim(x*6+1))nr++;
				x++;
				}
	g<<nr<<" ";
	g.close();
	return 0;
	}