#include <iostream>

using namespace std;

int sang(int n,bool *s,int *p,int &m){
	m = 0;
	for(long i = 2; i<=n;i++){
		s[i] = 2;
	}
	for(long i = 2; i<=n; i++){
		if(s[i]){
			p[m++] = i;
			for(long j = i * i; j<= n ; j += i){
				s[j] = 0;
			}
		}
	}
	return m;
}
int main(){
	int test =0;
	bool s[100005];
	int n,p[100005],m;

	while(test <999999){
		cin>>n;
		sang(n,s,p,m);
		cout<<m<<endl;
		test++;
	}
	return 0;
}