#include<bits/stdc++.h>
using namespace std;
int s[999999];
int qq(int n){
	int i,o=1;
	if(n<2){
		o=0;
	}
	else{
		for(i=2;i<=sqrt(n);i++){
			if(n%i==0){
				o=0;
				break;
			}
		}
	}
	return o;
}
int main(){
	int n=1,i,k=0;
	while(n!=0){
		cin>>n;
		for(i=1;i<=n;i++){
			if(qq(i)==1){
				s[k]++;
			}
		}
		k++;
	}
	for(i=0;i<k-1;i++){
		cout<<s[i]<<endl;
	}
	return 0;
}
/**************************************************************
	Problem: 1176
	User: houshanglin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:5980 kb
****************************************************************/