#include <iostream>

using namespace std;

int vtoad(int);

int main(void){
	char	*val;
	int	c,N,ad;

	while(cin >> N){
		c=2;
		val = new char[N/3+2];
		for(int i=0;i<N/3+2;i++)
			val[i]=0;

		for(int i=1;i*6-1<=N;i++)
			for(int j=-1;j<=1;j+=2)
				if(i*6+j<=N&&(ad=vtoad(i*6+j)))
					if(!val[ad]){
						c++;
						for(int k=2;(i*6+j)*k<=N;k++)
							if(ad=vtoad((i*6+j)*k))
								val[ad]=1;
				}
		cout << c << endl;

		delete [] val;
	}

	return 0;
}

int vtoad(int val){
	if(!((val+1)%6))
		return (val+1)/3-1;
	else if(!((val-1)%6))
		return (val-1)/3+2;
	else
		return 0;
}