[cpp]
#include
#include
int judge(int n)
{
int i,b;
b=(int)sqrt(n)+1;
for(i=2;i<=b;i++)
if(n/i*i==n)
return 0;
return 1;
}
int main()
int n,i,num;
scanf("%d",&n);
while(n)
{
num=0;
if(n==4)
printf("1\n");
else
{
for(i=3;i<=n/2;i+=2)
if(judge(i)&&judge(n-i))
num++;
printf("%d\n",num);
}
scanf("%d",&n);
}
}