#include <iostream>
#include <cmath>
#include <math.h>

using namespace std;

int SUUZI[1000000];

int a=0,b,d,f,n,c=0;
double buffer;

int main(){

	for(d=0;d<1000000;d++){SUUZI[d]=1;};
	
		for(a=3;a<1000000;a++){
			buffer=a;
				for(b=2;1;b++){
					if(a%b==0){SUUZI[a]=0;break;};
					if(b>sqrt(buffer)){SUUZI[a]=1;break;};
				};
};


cout<<c<<endl;

while(cin>>n){
	c=0;
for(d=0;d<=n;d++){c+=SUUZI[d];};

cout<<c-2<<endl;

};
return 0;

}