POJ-2909-Goldbach's Conjecture

#include<cstdio>
#include<cstring>
const int maxn=32800;
bool ispri[maxn];
int pri[maxn],cnt;
void Init()
{
ispri[1]=1;
cnt=0;
for(int i=2;i<maxn;i++)
{
if(!ispri[i])
pri[cnt++]=i;
for(int j=2;i*j<maxn;j++)
ispri[i*j]=1;
}
}
int main()
{
Init();
int n;
while(scanf("%d",&n)&&n)
{
int m=n>>1,ans=0;
for(int i=0;pri[i]<=m;i++)
if(!ispri[n-pri[i]])
ans++;
printf("%d\n",ans);
}
return 0;
}