/*   @JUDGE_ID:   1705PZ   686   C */
#include <stdio.h>
#include <stdlib.h>

int main(){
int count,pcount = 1,temp,answer;
long i,j,n;
long prime[3600];

prime[0] = 2;
for(i = 1;i < 16384;i++){
	temp = 0;
	for(j = 0;j < pcount;j++){
		if((i * 2 + 1) % prime[j] == 0){
			temp = 1;
			break;
			}
		}
	if(temp == 0)
		prime[pcount++] = i * 2 + 1;
	}

while(1){
	answer = 0;
	scanf("%ld",&n);
	if(n == 0)
		break;
	for(count = 0;count < pcount && prime[count] <= n;count++);
	for(i = 0;i <= count && prime[i] <= n / 2;i++)
		for(j = count;j >= i;j--)
			if(prime[i] + prime[j] == n)
				answer++;
	printf("%d\n",answer);
	}
return 0;
}
@END_OF_SOURCE_CODE