// #define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <cmath>
#include <cstdlib>
#include <functional>
#include <locale>
#include <cctype>
#include <sstream>
using namespace std;

typedef long long LL;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef map<int, int> MAPII;
typedef vector<pair<int, int> > VPII;

#define MP make_pair
#define fastIO	cin.tie(0); ios::sync_with_stdio(false);
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
//for gcc (未test)
// #define FOREACH_IT(it,c)	for(typeof(c)::iterator it=(c).begin(); it!=(c).end(); ++it)
//for Visual Studio
#define foreach_it(type,it,c) for(type::iterator it=c.begin(), c_end=c.end(); it!=c_end; ++it)

// ------------------- include, typedef, define END. -------------------

bool sosuuCheck(int n){
	if (n % 2 == 0)	return false;
	for (int i = 3;i<=sqrt((double)n);i+=2){
		if (n%i == 0)	return false;
	}
	return true;
}

int solve(int n){
	int ans = 0;
	for (int i = 3; i <= n / 2; i += 2){
		if (sosuuCheck(i)){
			if (sosuuCheck(n - i)){
				ans++;
			}
		}
	}
	return ans;
}

int main(){
	fastIO;
	int n;

	while (cin >> n, n){
		cout << solve(n) << endl;
	}
	return 0;
}