hdu 1397

#include<iostream>
#define Max 34000
using namespace std;
int a[Max];

void run()
{
	int i, j, k = 0;
	memset(a, true, sizeof(a));
	a[0] = a[1] = false;
	for(i = 2; i < Max; i++)
	{
		if(a[i])
		{
			for(j = i*i; j < Max; j+=i)
			{
				a[j] = false;
			}
		}
		
	}
}

int main()
{
	int n;
	run();
	while(scanf("%d", &n) != EOF && n)
	{
		int i, j, count = 0;
		for(i = 2;i <= n/2; i++)
		{
			if(a[i] && a[n-i])
				count++;
		}
		printf("%d\n", count);
	}

	return 0;
}