1 #include<iostream>
2 #include<stdio.h>
3 #define M 35000
4 #include<math.h>
5 #define N 3800
6 using namespace std;
7
8 int prime [N];
9 void give_list();
10 int main()
11 {
12 //freopen("acm.acm","r",stdin);
13 int i;
14 int j;
15 int num;
16 int sum;
17 give_list();
18 while(cin>>num)
19 {
20 sum = 0;
21 if(num == 0)
22 break;
23 for(i = 1; ;++ i)
24 {
25 for(j = i; ;++ j)
26 {
27 if(prime[i] + prime[j] == num)
28 ++ sum;
29 if(prime[i] + prime[j] > num)
30 break;
31 }
32 if(prime[i] >= num/2)
33 {
34 break;
35 }
36
37 }
38 cout<<sum<<endl;
39 }
40 }
41
42 void give_list()
43 {
44 int i;
45 int j;
46 bool prim1[M];
47 memset(prim1,true,sizeof(bool)*M);
48 prim1[1] = false;
49 for(i = 2; i < sqrt(long double(M))+1; i ++)
50 {
51 if(prim1[i])
52 {
53 j = 2*i;
54 while(j < M)
55 {
56 prim1[j] = false;
57 j += i;
58 }
59 }
60 }
61 j = 1;
62 for(i = 2; i < M; i ++)
63 {
64 if(prim1[i])
65 {
66 prime[j] = i;
67 ++ j;
68 }
69 }
70 }
